Monday, October 14, 2019

Habor Freight $4 Multimeter

I was generally pleased with Cen Tech multimeter from Habor Freight.  Similar looking multimeters (Item 63604) sold at Habor Freight now do not carry Cen Tech brand name; it can still be purchased for $3.99.  Upon close look the spec has changed a little bit,  The highest voltage only goes up to 250V DC or AC (vs 1000V), and the max current 5A (vs 10A).   It appears that the meter simply changed 1000V DC and 750V AC range to 250V range probably because of the fear of liability.  Opening it up, I can see the effort in cost reduction.  The Chip-on-Board I/C may be the same, but there are fewer discrete components and the PCB is smaller.   It does not have the trimmer. The fuse is soldered on; previously there was a fuse holder.  The probe is still decent; the spec says 18 gauge.  Even the critics now concede that the cheapest multimeters can be reasonably accurate; their main complaint is protections.   The CAT II rating cannot be taken serious; the CAT II marking on the probes are now removed.  One-mega-Ohm input impedance is also too much loading for some measurements.
The official spec is
  • 0-200mA: 1.2%+/-2d
  • 5A: 3%+/-5d
  • 200mV: 0.5%+/-1d
  • 2000mV-200V: 1%+/-2d
  • 250V: 1%+/-2d
  • AC 200/250V (45-450Hz): 1.2%+/-2d
  • No accuracy given for resistance
No spec for resistance measurements.

We'll check the accuracy against a Fluke 87 (spec voltage 0.05%, current 0.2%, resistance 0.2-0.6%).  The accuracy seems to have degraded somewhat, more so with the resistance measurements.  If you accept 1% error; it is OK for casual use.

Voltage
8.88.80.00%
48.949.10.41%
98.598.80.30%
149149.50.34%
198.5198.50.00%
4994990.00%
9999990.00%
19991992-0.35%
2.99930.03%
3.9994.010.28%
55.010.20%
99.020.22%
1212.020.17%
1515.020.13%
2019.97-0.15%
2525.20.80%
29.9930.20.70%
4040.30.75%
5050.40.80%
Current
17.817.7-0.56%
5454.10.19%
99.7100.10.40%
154154.50.32%
198.5198.90.20%
147014800.68%
195019690.97%
5.075.06-0.20%
10.2110.19-0.20%
15.3415.29-0.33%
19.619.52-0.41%
50500.00%
99.799.70.00%
150.8150.90.07%
197.3197.2-0.05%
0.50.50.00%
10.99-1.00%
21.99-0.50%
2.9992.99-0.30%
3.9993.99-0.23%
54.99-0.20%
660.00%
770.00%
* I took the current up to 7A; it is still working. I wonder if the lower spec is just to be on the conservative side.
 
Resistance
10.911.11.83%
50.750.70.00%
100.5100.3-0.20%
150.3149.6-0.47%
190.2189-0.63%
499494-1.00%
998987-1.10%
14961479-1.14%
18971872-1.32%
4.984.95-0.60%
9.999.92-0.70%
14.9814.85-0.87%
18.9818.79-1.00%
49.849.7-0.20%
99.299.1-0.10%
149148.7-0.20%
189188-0.53%
498493-1.00%
997989-0.80%
14941480-0.94%
18951872-1.21%

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