DM4070 LCR Meter Review

I have a need to measure home-wound inductors in the range of 10 – 100 μH (It’s for the power transfer controller of the solar bicycle).

On eBay, I found quite a few “universal” 12864 testers based on the atmega328 for as low as $13. Those would measure L, C, R, as well as semiconductors. However, I could find no spec in the descriptions for the inductance measurement range. The image here suggests that the maximum resolution is 0.01 mH (10 μH) – not really good enough if I want to distinguish between, say 13 μH and 18 μH.

My final choice was the DM4070. At $31.50 (US seller, free shipping), it was the cheapest LCR meter that would do what I needed.

flat-rate envelope
The DM4070 arrived in a flat-rate envelope.
generic box
The box is generic, showing some other models perhaps that leverage the same case. Who cares, I’m probably going to recycle the box, anyway.
box contents
The box contained the meter, a set of short alligator clip test leads, and a poorly-written manual.

Included with the meter was a poorly-written manual. Perhaps it was translated from Chinese? The translation was intelligible, as long as I used imagination.

torn boot
Although there was no shipping damage to the unit, one of the insulating boots on a test clip was torn. It’s still functional.
plastic stand
There is a plastic stand that swivels out on the back to hold the meter at an angle. The plastic was so flimsy, and so difficult to pull out, that I was afraid I was opening it the wrong way.

After the quick visual examination of the unit, I pressed the power button. Nothing. Maybe batteries weren’t included? I slipped off the shock case, removed a philips screw, and looked into the battery compartment.

battery compartment
Not good. I also cleaned up the tiny bit of corrosion on the case screw, for good measure.
dead 9V battery
Confirmed, the included battery is dead.

I put a fresh 9-volt battery in, and the DM4070 powered up fine. Fortunately, none of the chemical leakage from the battery appeared to have gotten into the actual device. I’m wondering: does the DM4070 go through batteries quickly? It’s supposed to automatically sleep after being idle for a few minutes, but I haven’t personally witnessed this behavior, yet. I’ve been turning the meter off after every use.

My first measurement was of a known inductor. I first shorted the test leads together to determine the lead inductance. Actually, the operation manual says not to do this, but I think that warning was intended for capacitance measurements, or perhaps to save power.

lead inductance
Before doing a low inductance measurement, I shorted the leads to see what their inductance would be.
HL-KK110U/BC 10 μH
After accounting for lead inductance of 1.4 μH, the measurement of this HL-KK110U/BC 10 μH inductor was spot-on.
transformer primary
The 220-volt primary of this torroidial transformer was over 12 Henries.

Next, I measured some capacitors. I tried a few and found the measurements to be mostly good. Possibly the measurements of high value capacitors were a little low. The DM4070 reported my 1000 μF capacitor as being 953 μF. I might have chalked that up to component tolerance, except that I had measured that lot of capacitors previously with my a test jig of my own design, and believed that they were more like 1100 μF.

cap trim knob
There’s a trim knob to null out test lead capacitance. It only applies to capacitance, however. For inductance and resistance, the user must mentally compensate.
loose integral clips
There are integrated slots which are supposed to accept direct insertion of components. The clips are too narrow to take a wire larger than about 16 gauge, yet too loose to hold most component leads firmly. Shown above is a 470 pF capacitor reading as 0.6 pF, until I jiggled it to make contact. It’s usable, but if there was one change I could make on this meter, it would be to substitute a higher quality clip.

Finally, I measured some resistors. The readings were quite accurate, except on the 20 MΩ range, where they seemed to read 5% high. Some of it might have been component tolerance. Actually, I’m pleased to have a 20 MΩ range at all – cheap digital voltmeters often top out at 2000 kΩ (2 MΩ). The 2 MΩ range is actually missing on this meter, so if you need to measure things in the hundreds of kΩ with precision, this is not the meter for you.

One thing that I noticed is that on the high value ranges, the readings took a few seconds to settle to a final value. This is fine, as long as one knows to wait.

Here are the test results:

Component Labeled Reading Notes
Inductor 10 μH -0+30% 9.6 μH After subtracting 1.4 μH for leads
Inductor 30 μH -0+30% 29.7 μH After subtracting 1.4 μH for leads
8.5V winding 43.9 mH torroidial transformer secondary
14.9V winding 150.7 mH torroidial transformer secondary
115V winding 3.27 H torroidial transformer primary
105V winding 2.59 H torroidial transformer primary
220V winding 12.35 H above 2 windings in series
Capacitor 75 pF 77.3 pF
Capacitor 470 pF 5% C0G .477 nF ceramic
Capacitor 2700 pF 5% 2.73 nF polystyrene
Capacitor 1 μF 1.001 μF ceramic
Capacitor 4.7 μF 5.05 μF solid tantalum
Capacitor 100 μF 96.3 μF aluminum electrolytic
Capacitor 470 μF 457 μF aluminum electrolytic
Capacitor 1000 μF 953 μF aluminum electrolytic
Resistor 0.62 Ω 1% 0.62 Ω After subtracting 0.08 Ω for leads
Resistor 11 Ω 5% 11.37 Ω After subtracting 0.08 Ω for leads
Resistor 137 Ω 1% 136.9 Ω
Resistor 562 Ω 1% .561 kΩ
Resistor 16.2 kΩ 1% 16.18 kΩ
Resistor 33 kΩ 5% 33.1 kΩ
Resistor 180 kΩ 5% .19 MΩ
Resistor 2.2 MΩ 5% 2.36 MΩ
Resistor 3.3 MΩ 5% 3.43 MΩ
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