Testing another Aliexpress Antenna

Below the results of the measurement of another Antenna. 

I did buy this antenna some time ago on AliExpress.

Testing Quansheng Antenna

When testing the gate fence antenna (see a previous post) i also wanted to compare the measured result with some other antenna's. This is the result of a quick measurement of an antenna that came with of one of my Quansheng 2m/70cm radio's.

Gate fence electronics dismantling -2- Testing gate fence antenna

Testing a gate fence antenna with a vector network analyzer. This is a picture of the antenna of the original receiver for the fence controller after some cleaning. ( See previous blogpost)

As i have a vector network analyzer (vna) i wanted to test the antenna to check on what frequencies it can be (re)used. I soldered an sma connector to the coax wire, calibrated the vna and did a quick scan over a relative broad range.

See below the results displaying Smith chart, Quality factor and swr (VSWR). The lower the swr the better. The minima in the swr curve give an indication of optimal frequencies.

I also did the same quick scan on some other antenna's and post the blog reports with the results.  Therefore this blogpost is in fact part of two different series of blog posts.

-1- Dismantling the electronics of a gate fence. ( #GateFence )
-2- Some antenna's quick tested ( with a vector network analyzer (vna) ).

Gate fence electronics dismantling -1- Main control and rx board

In this post some pictures of electronics in a 220 Volt gate controller to control 220 Volt motors.After many years of service this device was not working reliable anymore and i needed to replace it. This blogpost is also to document the old situation.

Top left you see a transformer top right are battery holders (not used) . In the middle of the picture you see the main controller board. Also you  can see a part of the antenna. However this remote control was not used.

The cable bundle on the right form a separate circuit with cables going to a light sensor for a lamp.

In this picture the mains to the control board is disconnected .(The wires where temporary placed in additional screw terminals connected to nothing to put the fence control temporary out of service).

Original the connection was to the left two connections where also the white wire on the left is connected. The white wire is to power a 433 MHz remote control switch box (bottom left). From this control box go wires to contacts on the main controller board to external contact to open and close the gate. Below a closeup of the control board after disassembling.

On the right is the connector for the receive module. Below some pictures of this module.

As already mentioned the control board is completely replaced with a new (different) board. I also removed the antenna and tested it with a vector network analyzer. You can see the bottom part of the antenna in the first picture of this post top right.
Results of antenna measurements will come in a next blogpost.

Measuring Resistance of Fuses with a Milliohm Meter and Kelvin Clips -4- (Self Resettable fuse )

Recently i received this 30A self resettable fuse via AliExpress.

As you can see on the pictures on one side is printed:

A                        (i don't know yet what this means)

Suppl. Prot. 
LINE  LOAD (to mark te connections).

On the other side of the self resettable fuse has the tekst

ZHONGZUI 78 Series 30A
125/250 VAC 50/60 Hz  50VDC 
TC3OL1/U3

And symbols suggesting that the fuse had passed some tests.

And yes i tested it with my Milliohm meter by connecting the Kelvin Clips.

The measured resistance was only 0.002 Ohm

I don't know what the resistance will be under normal use contions, however is was happy surprised with this low resistance !! 

Measuring Resistance of Fuses with a Milliohm Meter and Kelvin Clips -3- (More 12 Volt Fuses)

I received more 12 fuses and in this this blogpost i am going to present the results of the 12 Volt fuses. My intention was to publish after my post about the 250V glass fuses some evaluation of the data. However i received from Aliexpress a nice Anderson Powerpole connection block "DC 36V AP-8S 8 Channel Power Distributor For HF Radio Communication Power Supply Splitter Anderson Powerpole Screw Fixing" with more 12 Volt fuses. 

As i only had a few results of 12V fuses in my first post about the car fuses and i was curious about these Chinese fuses i gave more priority to measure the 12V fuses.

I want to do a separate blogpost about a review of this Anderson Powerpole block (and it also will appear in a mailbag blog) as i think it is a real nice power block that i bought for a decent price.  Not only does did it had a set of fuses in the block, also a spare set of fuses was included. 
So i now additional have 2 x ( 1x 40A + 3x 25A + 2x 15A + 1x 10A + 1x 5A ) fuses.

In the table below are also the results from the set car fuses already mentioned in the previous blog about the 12 V car fuses (= S1 [set1] ) and the fuse that came with the single fuse holder (= H1) . 

The measurement with this single fuse holder are not included as i wanted to focus this post on the fuse not on the fuse holder(s). 

Resettable Fuse Circuit Breaker

Via Aliexpress i also got a 12V 24V DC Car Truck Audio Resettable Fuse Circuit Breaker 30A Circuit Breaker. (see picture below) 

Resettable Fuse Circuit Breaker

A nice thing about this fuse is that you can reset it and it can be used as circuit breaker. ('Resettable Fuse Circuit Breaker'). I was curious about this fuse so i ordered one and included the result in the table below.  Pressing the circuit breaker and resetting the fuse (several times) gave each time the same resistance.
Spoiler alert: Relative to the other 30A fuse the resistance seems higher. However the resistance is still low.

Safety

Be aware that these resetable fuse circuit breakers (and also the normal 12V car fuses from AliExpress) have a bad reputation and can be unsafe.

The Carpoint fuses that i did buy at the Gamma  in The Netherlands are also made in China. (See packaging bottom right). 

Measurement

I removed fuses (one by one) from the Anderson Powerpole block and measured the resistances ( Ab to Ab7 [the number corresponds with the number on the Anderson Powerpole block ] ). I was a little difficult to remove these fuses. 

The spare fuses that came with the Anderson Powerpole block ( Ax to Ax7 ) where also measured.

The results

Table 1: Results 12V fuses (Including previous results, sorted on rated current). 

Fuse	Color	Rated Current	Measured Resistance	Calculated Voltage drop at 100 mA	Calculated Voltage drop at rated current	Calculated Voltage drop at rated current in % relative to 12 Volt
Ab7	Biege	5	0.014	0.0014	0.070	0.58%
Ax7	Biege	5	0.013	0.0013	0.065	0.54%
S1	Brown	7.5	0.009	0.0009	0.068	0.56%
Ab6	Red	10	0.006	0.0006	0.060	0.50%
Ax6	Red	10	0.006	0.0006	0.060	0.50%
H1	Red	10	0.007	0.0007	0.070	0.58%
S1	Red	10	0.006	0.0006	0.060	0.50%
Ab4	Blue	15	0.004	0.0004	0.060	0.50%
Ab5	Blue	15	0.004	0.0004	0.060	0.50%
Ax4	Blue	15	0.005	0.0005	0.075	0.63%
Ax5	Blue	15	0.005	0.0005	0.075	0.63%
S1	Blue	15	0.004	0.0004	0.060	0.50%
S1	Yellow	20	0.003	0.0003	0.060	0.50%
Ab1	Clear	25	0.002	0.0002	0.050	0.42%
Ab2	Clear	25	0.003	0.0003	0.075	0.63%
Ab3	Clear	25	0.003	0.0003	0.075	0.63%
Ax1	Clear	25	0.003	0.0003	0.075	0.63%
Ax2	Clear	25	0.003	0.0003	0.075	0.63%
Ax3	Clear	25	0.003	0.0003	0.075	0.63%
S1	Clear	25	0.002	0.0002	0.050	0.42%
Resettable  Fuse Circuit Breaker	(*1)	30	0.004	0.0004	0.120	1.00%
S1	Green	30	0.002	0.0002	0.060	0.50%
Ab	Amber	40	0.001	0.0001	0.040	0.33%
Ax	Amber	40	0.001	0.0001	0.040	0.33%

Summary

Higher rated fuses seem to have a lower resistance.

Between 12 Volt fuses of the same rating is not much variation in the resistance.

The 30 A Resettable Fuse Circuit Breaker seems to have a higher resistance (and higher voltage drop) than a standard 30A 12V fuse.

Also, compared to the 250 Volt fuses in my previous post these 12V car fuses have a much lower resistance !!!

Measuring Resistance of Fuses with a Milliohm Meter and Kelvin Clips -2- (250V Fuses measurement results )

Ensuring the integrity and reliability of 250V fuses is crucial for maintaining the safety and functionality of high-voltage electrical systems. In this post, I'll share my experience measuring the resistance of 250V fuses using an affordable milliohm meter equipped with Kelvin clips, highlighting the key considerations and benefits of this method.

Why Measure Fuse Resistance?

Regularly measuring the resistance of 250V fuses is essential for several reasons:

1. Ensuring Reliability:

Over time, fuses can develop higher resistance due to aging or exposure to harsh conditions.

2. Troubleshooting:

Identifying a fuse with abnormal resistance can help diagnose and prevent circuit issues.

3. Preventive Maintenance: 

Regular measurements allow for the replacement of fuses before they fail, avoiding potential downtime or damage.

Tools Needed

For this task, I used:

- Milliohm Meter:

 Capable of measuring low resistance values accurately.

- Kelvin Clips: 

Four-wire probes that eliminate the influence of lead and contact resistance, providing precise measurements.

The Measurement Process

Here's a quick overview of the process:

1. Calibration:

Ensure the milliohm meter is calibrated using the shorting clip and zeroing function.

2. Connecting Kelvin Clips: 

Attach the clips to the fuse, ensuring a solid, clean connection at opposite ends.

3. Taking the Measurement: 

Power on the meter and read the displayed resistance value.

Voltage Drop Across the Fuse

For a milliohm meter with a measurement current of 100 mA, the voltage drop across the fuse can be calculated using Ohm's Law (V = I × R).

Example Calculation:

- For a measured resistance of 0.005 ohms: 

  - Voltage Drop: V = 100 mA × 0.005 ohms = 0.5 mV

- For a measured resistance of 0.002 ohms: 

  - Voltage Drop: V = 100 mA × 0.002 ohms = 0.2 mV

Change in Resistance Due to Heating

When a fuse is subjected to higher currents, it can heat up, causing its resistance to change:

- Initial Resistance:

The resistance at room temperature is relatively low.

- Heating Effect:

Higher current flow increases temperature, raising the resistance.

- Increased Resistance:

This change can be significant, especially for currents near the fuse’s rated limit.

Measured resistance

I having a long time a box with slow 250V glass fuses with values 50 mA, 160 mA, 200 mA, 315 mA, 500 mA, 800 mA, 1 A, 2 A, 2.5 A. It would be nice to use these fuses as a test-set. 

My box with fuses (open)

I first did think it was needed to measure each fuse several times. However during my first (not documented) test i discovered that remeasuring a fuse id almost gave no variation in the result. (max 1 or 2 in the last digit).  The variation between different fuses of the same rating was much bigger. Therefore i decided to measure all the fuses once and put the results in a table (1).

However there were some limitations: 

- According to the manual, the resistance is measured with a testing current of about 100 mA. ( i did not check this yet.) Therefore i decided to skip to 50 mA fuses as they would be blown an not measured.

- The fuses are relative old. I expect at least 25 years. The nice thing is that it is a set of in total more than 140 fuses of different values and the aging effect of the fuses is included.

- The box with fuses had at (least) two sources. A box with fuses that i did buy many years ago and a similar box with fuses that i received some year ago from someone else. I did merge the content of these boxes a year ago to save some space.

- I noticed some fuses had a resistance far above 1 ohm. (And i expect some of these fuses where bad. I measured with a multi-meter around 200 Ohm and some above 10 Mega Ohm and even some fuses that made no connection at all. I removed these fuses from the box with fuses, kept them apart and did not include the results. I expect the fuses that made no connection at all are blown fuses and i did throw them away.  

- All my 2.5 A fuses had corrosion and the measured resistances where above 1 Ohm. I don't know if this is normal or this was due to aging and/or the corrosion. The strange thing is that all the 2.5 A fuses that had visible corrosion and almost none of the other fuses.  I don't know the source of the corrosion. Perhaps the fuses are of a different material or there was humidity that mainly reached the 2.5 A fuses and not the other fuses. Therefore i excluded all of the 2.5 A fuses.

Results

Below a table with the measured resistance , the calculated voltage drop at 100mA and the voltage drop at the rated current.

Table 1: Measured resistances with calculated voltage drops

Result /  measurement Number	mA	Measured  resistance	Calculated Voltage drop at 100mA	Calculated Voltage drop at rated current
1	500	0.447	0.04470	2.235
2	500	0.477	0.04770	2.385
3	500	0.446	0.04460	2.230
4	500	0.434	0.04340	2.170
5	500	0.520	0.05200	2.600
6	500	0.461	0.04610	2.305
7	500	0.510	0.05100	2.550
8	500	0.536	0.05360	2.680
9	500	0.462	0.04620	2.310
10	500	0.432	0.04320	2.160
11	500	0.502	0.05020	2.510
12	500	0.482	0.04820	2.410
13	500	0.452	0.04520	2.260
14	500	0.465	0.04650	2.325
15	500	0.424	0.04240	2.120
16	500	0.456	0.04560	2.280
17	500	0.469	0.04690	2.345
18	500	0.461	0.04610	2.305
19	160	0.579	0.05790	0.926
20	160	0.570	0.05700	0.912
21	160	0.537	0.05370	0.859
22	160	0.640	0.06400	1.024
23	160	0.409	0.04090	0.654
24	160	0.658	0.06580	1.053
25	160	0.664	0.06640	1.062
26	160	0.531	0.05310	0.850
27	160	0.613	0.06130	0.981
28	160	0.568	0.05680	0.909
29	160	0.677	0.06770	1.083
30	160	0.581	0.05810	0.930
31	160	0.604	0.06040	0.966
32	160	0.619	0.06190	0.990
33	160	0.494	0.04940	0.790
34	160	0.615	0.06150	0.984
35	160	0.689	0.06890	1.102
36	160	0.557	0.05570	0.891
37	160	0.409	0.04090	0.654
38	160	2.900	0.29000	4.640
39	1000	0.088	0.00880	0.880
40	1000	0.089	0.00890	0.890
41	1000	0.092	0.00920	0.920
42	1000	0.087	0.00870	0.870
43	1000	0.089	0.00890	0.890
44	1000	0.089	0.00890	0.890
45	1000	0.087	0.00870	0.870
46	1000	0.089	0.00890	0.890
47	1000	0.087	0.00870	0.870
48	1000	0.094	0.00940	0.940
49	1000	0.091	0.00910	0.910
50	1000	0.096	0.00960	0.960
51	1000	0.089	0.00890	0.890
52	1000	0.087	0.00870	0.870
53	1000	0.089	0.00890	0.890
54	1000	0.092	0.00920	0.920
55	1000	0.091	0.00910	0.910
56	1000	0.090	0.00900	0.900
57	1000	0.090	0.00900	0.900
58	315	0.700	0.07000	2.205
59	315	0.562	0.05620	1.770
60	315	0.761	0.07610	2.397
61	315	0.706	0.07060	2.224
62	315	0.852	0.08520	2.684
63	315	0.805	0.08050	2.536
64	315	0.607	0.06070	1.912
65	315	0.723	0.07230	2.277
66	315	0.681	0.06810	2.145
67	315	0.612	0.06120	1.928
68	315	0.646	0.06460	2.035
69	315	0.884	0.08840	2.785
70	315	0.760	0.07600	2.394
71	315	0.719	0.07190	2.265
72	315	0.871	0.08710	2.744
73	315	0.766	0.07660	2.413
74	315	0.681	0.06810	2.145
75	315	0.620	0.06200	1.953
76	315	0.759	0.07590	2.391
77	315	0.602	0.06020	1.896
78	2000	0.039	0.00390	0.780
79	2000	0.039	0.00390	0.780
80	2000	0.039	0.00390	0.780
81	2000	0.042	0.00420	0.840
82	2000	0.038	0.00380	0.760
83	2000	0.037	0.00370	0.740
84	2000	0.035	0.00350	0.700
85	2000	0.703	0.07030	14.060
86	200	0.331	0.03310	0.662
87	200	0.485	0.04850	0.970
88	200	0.545	0.05450	1.090
89	200	0.405	0.04050	0.810
90	200	0.486	0.04860	0.972
91	200	0.584	0.05840	1.168
92	200	0.490	0.04900	0.980
93	200	0.573	0.05730	1.146
94	200	0.472	0.04720	0.944
95	200	0.442	0.04420	0.884
96	200	0.446	0.04460	0.892
97	200	0.508	0.05080	1.016
98	200	0.515	0.05150	1.030
99	200	0.429	0.04290	0.858
100	200	0.489	0.04890	0.978
101	200	0.395	0.03950	0.790
102	200	0.491	0.04910	0.982
103	250	0.268	0.02680	0.670
104	250	0.517	0.05170	1.293
105	250	0.382	0.03820	0.955
106	250	0.388	0.03880	0.970
107	250	0.385	0.03850	0.963
108	250	0.340	0.03400	0.850
109	250	0.348	0.03480	0.870
110	250	0.366	0.03660	0.915
111	250	0.249	0.02490	0.623
112	250	0.322	0.03220	0.805
113	250	0.338	0.03380	0.845
114	250	0.405	0.04050	1.013
115	250	0.263	0.02630	0.658
116	250	0.361	0.03610	0.903
117	250	0.350	0.03500	0.875
118	250	0.247	0.02470	0.618
119	250	0.349	0.03490	0.873
120	250	0.322	0.03220	0.805
121	250	0.342	0.03420	0.855
122	250	0.371	0.03710	0.928
123	250	0.292	0.02920	0.730
124	800	0.151	0.01510	1.208
125	800	0.136	0.01360	1.088
126	800	0.139	0.01390	1.112
127	800	0.127	0.01270	1.016
128	800	0.133	0.01330	1.064
129	800	0.131	0.01310	1.048
130	800	0.141	0.01410	1.128
131	800	0.128	0.01280	1.024
132	800	0.128	0.01280	1.024
133	800	0.133	0.01330	1.064
134	800	0.136	0.01360	1.088
135	800	0.143	0.01430	1.144
136	800	0.127	0.01270	1.016
137	800	0.128	0.01280	1.024
138	800	0.135	0.01350	1.080
139	800	0.136	0.01360	1.088
140	800	0.132	0.01320	1.056
141	800	0.147	0.01470	1.176
142	800	0.132	0.01320	1.056

Some of the fuses gave results that made me doubt if the fuse had indeed the current rating i expected. However i did check the rating it on the fuse! 

Table 2: Summary of measured resistances  (Some outliers are removed.)

Fuse rating (mA)	Average resistance	Min resistance	Max resistance
160	0.5797	0.409	0.689
200	0.4756	0.331	0.584
250	0.3431	0.247	0.517
315	0.7159	0.562	0.884
500	0.4687	0.424	0.536
800	0.1349	0.127	0.151
1000	0.0898	0.087	0.096
2000	0.0384	0.035	0.042

 

Fuses with a higher rating seem to have a lower resistance, however even in this box with fuses not always!  I decided to already publish the measured results with a quick summary. In an upcoming blog-post i will do a more in depth evaluation of the results.

My box with fuses (closed)

Conclusion

Measuring the resistance of 250V fuses with a milliohm meter and Kelvin clips is a straightforward yet powerful method to ensure the health of your high-voltage circuit protection devices. Regular checks can help you catch potential issues early, maintaining the integrity and safety of your electrical systems. It was also a good exercise to measure these fuses to check the health and variation between these fuses. This affordable and accurate setup is a valuable addition to any toolkit, providing peace of mind and reliable performance.

Stay tuned for more insights and results from my ongoing experiments and measurements and a more in-depth evaluation of these measured results. Happy measuring!

Measuring Resistance of Fuses with a Milliohm Meter and Kelvin Clips -1- ( Car fuses )

In the world of electronics, ensuring the integrity of fuses is crucial for the safety and reliability of circuits. Fuses act as protective devices, preventing excessive current from damaging components. Over time, however, fuses can degrade, leading to increased resistance, which may compromise their effectiveness. Today, I'll share my experience measuring the resistance of some 12 Volt car fuses using an affordable milli-ohm meter equipped with Kelvin clips. This method provides accurate results, essential for maintaining optimal circuit performance.

Why Measure Fuse Resistance?

Measuring the resistance of fuses serves several purposes:

1. Ensuring Reliability: 

Over time, fuses can develop higher resistance due to aging or exposure to harsh conditions. Regular checks ensure they are still effective.

2. Troubleshooting: 

Identifying a fuse with abnormal resistance can help diagnose and prevent circuit issues.

3. Preventive Maintenance:

Regular measurements allow for the replacement of fuses before they fail, avoiding potential downtime or damage.

Equipment Needed

For this task, I used the following equipment:

- Milliohm Meter: 

A device capable of measuring low resistance values accurately. I used a YMC01 2R handheld Milliohm Meter. For details see my previous blogpost. According to the manual this meter uses a testing current of about 100 mA (i did not check this),

- Kelvin Clips:

 Four-wire probes that eliminate the influence of lead and contact resistance, providing precise measurements. These where included with my meter.

- Fuses:

 For the first test i used some some new 12 Volt Car fuses.

Also i tested a fuse in a fuse holder.

Below a table of the color codes of the car fuses.

The Measurement Process

Here’s a step-by-step guide to measuring fuse resistance with a milliohm meter and Kelvin clips:

1. Calibration

Before starting, it’s essential to calibrate the milliohm meter. Follow these steps:

- Turn on the meter and allow it to stabilize.

- Use the provided shorting clip to connect the Kelvin clips together.

- Zero the meter according to the manufacturer’s instructions. This step ensures that the meter reads zero when there’s no resistance. My cheap meter does not have a zeroing function. H

2. Connecting Kelvin Clips

Attach the Kelvin clips to the fuse. Ensure a solid, clean connection:

- Place the clips at opposite ends of the fuse to measure the resistance accurately.

- Make sure there is no dirt or oxidation on the fuse terminals that could affect the reading.

3. Taking the Measurement

With the Kelvin clips properly connected, take the reading:

- Power on the meter.

- Read the displayed resistance value. The milliohm meter should provide a precise measurement free from lead resistance thanks to the Kelvin clips.

Voltage Drop Across the Fuse

For your milliohm meter with a 0-1 ohm range and a measurement current of 100 mA, you can calculate the voltage drop across the fuse using Ohm's Law (U = I × R).

Example Calculation:

1. Voltage drop at 100 mA : 

   - 100 mA = 0.1 Ampere

   - Measured Resistance: 0.004 ohms

   - Voltage Drop: U = 0.1 A × 0.004 ohms = 0.0004 volts (0.4 mV)

2. Voltage drop at current rate:

   - Fuse rating (e.g. 15 Ampere )

   - Measured Resistance: 0.004 ohms

   - Voltage Drop: U = 15 A × 0.004 ohms = 0.060 volts (30 mV)

2. Relative Voltage drop at current rate:

A voltage drop of 0.060 volts is at 12 Volt the relative voltage drop of 100% * 0.060/12 = 0.50 % 

Change in Resistance Due to Heating

When a fuse is subjected to higher currents, it can get hot, causing its resistance to change. This phenomenon is due to the temperature coefficient of resistance, which describes how the resistance of a material changes with temperature. For most metals, resistance increases as temperature increases.

Key Points:

1. Initial Resistance:

 The resistance of a fuse at room temperature is relatively low.

2. Heating Effect: 

As current flows through the fuse, it heats up. The amount of heat generated is proportional to the square of the current (P = I²R).

3. Increased Resistance: 

As the temperature of the fuse rises, so does its resistance. This change can be significant, especially for currents near the fuse’s rated limit.

Example:

If a fuse rated for 1A is subjected to a current close to its limit, it will heat up. The resistance can increase noticeably, potentially doubling or tripling depending on the fuse material and the current applied.

My Measurement Results

For this first test a set of 12 Volt Car fuses (see pictures above) and a 10A fuse with a fuse holder was used.

Table with Results:

Fuse	Rated Current	Measured Resistance	Calculated Voltage Drop (100 mA)	Calculated Voltage Drop at rated current	Calculated Voltage drop at rated current in % relative to 12 Volt
10A (without fuse holder)	10   A	0.008	0.0008	0.08	0.67 %
10A fuse in fuse holder	10   A	0.007	0.0007	0.07	0.58 %
Brown	7.5 A	0.009	0.0009	0.0675	0.56 %
Red	10   A	0.006	0.0006	0.06	0.50 %
Blue	15   A	0.004	0.0004	0.06	0.50 %
Yellow	20   A	0.003	0.0003	0.06	0.50 %
Clear	25   A	0.002	0.0002	0.05	0.42 %
Green	30   A	0.002	0.0002	0.06	0.50 %

Interpreting the Results

- Expected Values:

 Typically, a good fuse should have a very low resistance, often just a few milliohms.

- Anomalies: 

If a fuse shows significantly higher resistance than expected, it might be compromised and should be replaced.

Summary

These resistances are measured with the Milliohm meter. I expect all with around the same current of 100 mA. A higher current will heat up the fuse wire and change the resistance and to get real good conclusions other measurements will be needed. 

The measured resistances of these car fuses where very low (below 0.01 milliohm).

I only had two red 10A fuses (and for the other fuses only one) I measured a resistance of 0.0008 and 0.0006 for these fuses (and 0.0007 ohm for the first red fuse using the fuse holder),

The fuse holder did not add a significant resistance.

The lower rated fuses seem to have a slight higher resistance.

Measuring fuse resistance with a milliohm meter and Kelvin clips is a straightforward yet powerful method to ensure the health of your circuit protection devices. Regular checks can help you catch potential issues early, ensuring your electronics remain safe and functional. By investing in this affordable yet accurate setup, you can maintain the integrity of your circuits and prevent unexpected failures.

Stay tuned for more insights and results from my ongoing experiments and measurements. Happy measuring!

Discovering Precision on a Budget: Milliohm Meter with Kelvin Clips

When it comes to precise measurements of low resistance, having the right tools is essential. For electronics enthusiasts, hobbyists, and professionals, a milliohm meter is an invaluable addition to the toolkit. The good news is, you don't have to break the bank to get your hands on one. Today, we're diving into the world of affordable milliohm meters, specifically those that come with Kelvin clips and can be found for around 20 euros online.

What is a Milliohm Meter?

A milliohm meter is a specialized device used to measure very low resistance values, typically in the milliohm range (1 milliohm = 0.001 ohms [ Ω ]). These measurements are crucial in applications where even slight resistance variations can impact performance, such as in high-precision circuits, power electronics, and battery testing.

Why You Can't Use a Standard Multimeter and Need a Milliohm Meter

Standard multimeters, while versatile and useful for many applications, fall short when it comes to measuring very low resistances accurately. This limitation arises primarily because multimeters typically use a two-wire measurement method, which includes the resistance of the test leads and contact resistance in the reading. This added resistance can introduce significant errors, especially when measuring resistances in the milliohm range. Additionally, standard multimeters often lack the sensitivity and resolution needed to detect small changes in low resistance values. In contrast, a milliohm meter, equipped with Kelvin clips, eliminates the influence of lead and contact resistance, providing precise and reliable low-resistance measurements. This accuracy is essential for applications like testing fuses, where even slight variations in resistance can be critical.

The Role of Kelvin Clips

Kelvin clips, also known as four-wire probes, are essential for accurate low-resistance measurements. They use a four-terminal sensing method that eliminates the influence of lead and contact resistance. This is achieved by using separate pairs of leads for current supply and voltage measurement, ensuring that the voltage drop is measured directly across the component under test, free from extraneous resistance.

Why Shop Online?

Online marketplaces like AliExpress, offer a wide range of affordable electronics and tools, including milliohm meters equipped with Kelvin clips. These devices, often available for about 20 euros, might not match the high-end precision instruments in terms of build quality or advanced features but offer impressive accuracy and functionality for their price point.

Features to Look For

When shopping for a milliohm meter with Kelvin clips, consider the following features:

1. Measurement Range:

 Ensure the meter can measure the range of resistances you anticipate working with. Most budget meters will cover a range from milliohms to a few ohms.

2. Display:

 Look for a clear, easy-to-read display. Digital displays with backlighting can be particularly useful.

3. Accuracy:

 Check the accuracy specifications. While budget meters may not match laboratory-grade instruments, look for models with tolerances within 1% for general use.

4. Build Quality:

 While it’s hard to gauge build quality from pictures, look for customer reviews and ratings. This can provide insights into the durability and reliability of the meter.

5. Ease of Use:

 Features like auto-ranging, hold functions, and zeroing capabilities can make the device much more user-friendly.

Getting Started with Your New Meter

Once your milliohm meter arrives, here’s a quick guide to get you started:

1. Calibration:

 Before making any measurements, it's good practice to calibrate your meter according to the manufacturer’s instructions. This often involves zeroing the meter using the included shorting clip.

2. Connecting Kelvin Clips:

 Attach the Kelvin clips to the component you're measuring. Ensure a solid, clean connection to avoid any contact resistance that could skew your results.

3. Taking Measurements:

 Power on the meter and take your reading. The four-wire method employed by Kelvin clips will provide a direct measurement of the resistance, minimizing external influences.

4. Interpreting Results:

 Compare your readings with expected values. If you're testing components, ensure they fall within their specified tolerance ranges.

Pros and Cons

Pros:

- Affordability:

 For around 20 euros, these meters provide exceptional value for money.

- Functionality:

 Despite their low cost, they offer the essential features needed for accurate low-resistance measurements.

- Portability:

 Compact and lightweight, these meters are easy to carry and store.

Cons:

- Build Quality: 

Lower-cost meters may not be as durable or robust as higher-end models.

- Accuracy: 

While generally good, they might not match the precision of professional-grade instruments.

- Support and Documentation: 

Sometimes, the instructions and support can be lacking, requiring a bit of trial and error to master the device.

My Milliohm Meter

On Aliexpress i found two versions of the YMC01 milliohm meter.
The 2R model for the 1-1999 mΩ range and the 20R model for the 0.01-19.99 mΩ range.
I decided to go for the 2R, Ordering details will come in my mailbag post, Below is a screenshot of the manual. This is a A4 with on one side the Chinese manual and on the other side the English version.

On this meter there is no special button or something for calibration. I only found in the manual "Inserted 3196 potentiometer, user can do self-calibration." and "Automatically reset to 0". When connecting the two wires the meter displays indeed 0.000. (I expect the potentiometer is inside the housing, i did not yet opened it.)

One of the experiments i want to do with this meter is measure resistance of fuses. I want to make some separate blogposts about the results.

When reading the manual i found an important parameter for this measurement; the testing current: about 100 mA for the 2R and about 10 mA for the 20R. As i have 2R with testing current of 100 mA i will not be able to measure fuses of 100 mA or below as the fuse will blow.

Conclusion

A milliohm meter with Kelvin clips offers an affordable entry point into precise resistance measurement. While they may come with some limitations, these budget-friendly tools are perfect for hobbyists and those looking to add a useful device to their toolbox without spending a fortune. With careful use and proper handling, these meters can provide accurate measurements that meet the needs of various applications. Happy measuring!

Why My Next Self-Driving ( Electric ) Car Will Need a Drone

In the rapidly evolving world of automotive technology, the future is not just about electric or self-driving cars. It’s about integrating these advancements with other cutting-edge technologies to create an unparalleled driving experience. One of the most exciting innovations on the horizon is the combination of self-driving electric cars with drones. Here’s why my next car will be a self-driving (electric) vehicle equipped with a drone and what benefits this futuristic pairing can bring.

AI(NightCafe Studio) generated illustration for this blogpost

Enhanced Safety and Security

1. Surveillance and Monitoring:

   - A drone can be deployed to scout ahead on unfamiliar or potentially dangerous routes, identifying hazards such as roadblocks, accidents, or adverse weather conditions, allowing the autonomous vehicle to take alternate routes or prepare accordingly.

   - In parking lots or unfamiliar neighborhoods, a drone can provide an aerial view to ensure the area is safe before the car drops you off.

2. Emergency Assistance:

   - In case of an accident or breakdown, a drone can quickly fly to the scene to assess the situation and provide real-time information to emergency services. It can also project warnings on the road to alert other drivers, significantly reducing the risk of secondary accidents.

   - The drone can be automatically launched in the event of a severe accident, assisting emergency rescuers by providing aerial footage and locating injured passengers, thereby improving response times.

Convenience and Efficiency

1. Parking Assistance:

   - One of the major challenges of urban driving is finding a parking spot. A drone can scout for free parking lots ahead of your arrival, communicating directly with the car to guide it to the nearest available space. This feature can save time and reduce the stress of finding parking in crowded areas.

2. Navigation Aid:

   - When driving through congested urban areas or complex road networks, a drone can provide a bird’s-eye view of the traffic situation, helping the car’s navigation system plot the most efficient route.

   - For off-road adventures, a drone can scout the terrain ahead, identifying the best paths and avoiding obstacles that might be difficult to spot from the ground.

3. Connectivity Enhancement:

   - In areas with poor GSM or internet connectivity, the drone can fly high to act as a communication relay, ensuring that the car remains connected to essential services and navigation aids.

Enhanced Driving Experience

1. Entertainment:

   - For those long road trips, a drone can capture stunning aerial footage of the landscapes you’re driving through, providing a unique perspective and enhancing your travel experience. This footage can also be shared in real-time with friends and family, making your journey more interactive and engaging.

2. Personal Assistance:

   - A drone can be used for personal tasks such as retrieving items from a distance. Forgot your keys at a friend’s place? Your car’s drone can fetch them for you.

   - For the tech-savvy, drones can be integrated with smart home systems, enabling them to perform tasks like checking on your property or delivering items within your home network.

Advanced Communication and Connectivity

1. Vehicle-to-Drone Communication:

   - When your car and drone are in constant communication, the possibilities are endless. For example, the drone can provide live traffic updates directly to the car’s dashboard, enhancing situational awareness and decision-making.

   - In the event of a car theft, the drone can track the vehicle’s location and provide real-time updates to law enforcement, increasing the chances of recovery.

2. Projection Capabilities:

   - In emergency situations, the drone can project warnings or signals onto the road to alert other drivers of hazards ahead. This feature can help prevent accidents and ensure that emergency vehicles can navigate through traffic more efficiently.

Practical Considerations

1. Speed and Charging:

   - The drone, while incredibly useful, cannot fly as fast as the car can drive. Therefore, it will be parked and charged on or in the car when not in use. This ensures that it is always ready for deployment when needed.

   - The integration of a dedicated charging station for the drone within the car ensures it remains operational without requiring separate charging infrastructure.

Future Prospects

The integration of drones with self-driving electric cars is not just a fleeting trend but a glimpse into the future of mobility. As technology continues to advance, we can expect even more innovative uses for this combination. From enhanced safety and security to unparalleled convenience and a more enriched driving experience, the benefits of having a drone-integrated, self-driving electric car are manifold.

In conclusion, the addition of a drone to your self-driving electric car is more than just a high-tech gimmick; it’s a transformative feature that can significantly enhance your driving experience. Whether it’s for safety, convenience, or sheer enjoyment, the drone-car duo is set to redefine what we expect from our vehicles. So, when it’s time to choose your next car, consider one that comes with a drone – it might just be the smartest decision you make.