Der-EE DE-5000 LCR Meter Calibration and Adjustment

[MaxFrister]

I have a Der EE DE-5000 that I've used for a few years mostly for repairs. Since I mostly used it for go/no-go capacitor testing, it never occurred to me to check its accuracy.

Recently I was working on some speaker crossovers that required accurate inductor readings.  I kept finding inductors that were out of stated tolerance.  I finally checked with a different meter and they were in spec but the Der-EE was reading ~20% high.

I checked some caps and found the Der-EE reading high most of the time.

So, has anyone else noticed inaccurate readings with this meter? 

Has anyone found a procedure to calibrate and adjust it?

[RolandK]

Hi,
which Adapter do you use?
did you make the open short calibration according to the manual?
What Condensators did you meassure?
Which frequency did you use on the deree and what is the other meter and which frequency did you use there?
Regards.

[mnementh]

My first guess is this primarily has to do with a mismatch in the frequency the DE5000 is using vs that at which the inductors in question were tested when the specs were written. I find that when I choose a test frequency which is appropriate to the application (or as close as is possible); ie, 100/120Hz for iron core chokes meant to be used in 50-60Hz power supply vs 10-100KHz for ferrite inductors used in SMPS & RF, that the numbers are quite a bit closer.

Also... it is my experience that especially with cheap components as used in China-direct electronic projects... the rating stamped on inductors is very much like Barbossa's interpretation of the Pirate Code: More guidelines than actual rules. 

mnem
As usual, take what I say here with a pinch of salt big enough to pickle a dragon.

[coromonadalix]

And    at each startup  do an open and closed leads calibration ...

[MaxFrister]

The speakers were finished a few months back so I'm a bit hazy on the experimental method.

It sounds like the building consensus is operator error.  I'll borrow a bridge and make some more measurements tonight or tomorrow.

[armandine2]

If you had said, that you calibrate prior to use, the calibrate prior to use comments would not have come up in your replies, perhaps.

there is an eevblog teardown - don't remember seeing any adjustments there, but might be worth looking at.

[MaxFrister]

I ran a more systematic experiment but had similar results.   I’m at a bit of a disadvantage since I no longer have a new and measured inductor nor a calibrated meter to compare to.  I do have a box full of old inductors and 2 other (uncalibrated) meters.

Summary: Four different inductors were tested. The 2 meters tend to agree with each other and the DE-5000 is reading significantly different.  Changing leads, test frequency, or series/parallel on the DE-5000 does not significantly change readings.


Equipment:

Der EE DE-5000 LCR meter with modified TL-21 leads and no leads.  Open/Short lead calibration before each reading.
Sinometer VC6243+
Leader LCR-740 LCR Bridge

Subject A: Air-core inductor

DE-5000,  TL-21 modified leads, 1kHz
   0.791mH (Ls)
   0.793mH (Lp)

DE-5000, no leads
   0.793mH (Ls)
   0.795mH (Lp)

VC6243+ ~2.25kHz (not adjustable)
   0.962mH

LCR-740 1Khz
   0.962mH

Subject B: Ferrite core

DE-5000 No Leads
   1.3mH   (Ls, 100Hz)
   1.28mH (Ls, 1kHz)
   1.16mH (Ls, 10kHz)
   
VCG6243+
   1.52mH

LCR-740
   1.51mH

Subject C: Air core

DE-5000
   0.448mH (Ls)
      
VC6243+
   0.543mH

LCR-740
   0.544mH

Subject D: 14AWG foil inductor marked 0.47

DE-5000
   0.394mH

VC6243+
   0.467mH

LCR-740
   0.480mH

[The Electrician]

What do you get if you compare readings of a film capacitor of various values?

[MaxFrister]

What do you get if you compare readings of a film capacitor of various values?

Subject A: 20pF (2%)

DE-5000:    19.749pF
LCR-740:     19.7

Subject B: 200pF (1%)

DE-5000:   200.7pF
LCR-740:    201 pF


Subject C: 50nF film

De-5000: 631nF
LCR-740: 510.nF

Subject D: 25uF Electrolytic (5%)

DE-5000:    31.0
LCR-740:    25.1

[MaxFrister]

For completeness I thought I'd check resistance.

Using GR 1433B (1% decade) I get reasonable readings above 1K and ~20% low bellow 1K.  Interesting enough I can get both good and bad readings at 1k depending upon the direction I'm adjusting.  From bellow, I get 813 ohms, from above 999.6 ohms.

Starting to look more like a repair rather than an adjustment will be necessary.

[The Electrician]

There is apparently a range problem.  It's accurate on some ranges and not on others.  I don't think that's something you can fix. 

[toli]

A long shot, but is the battery voltage still OK?
I've had a similar problem with a dmm in the past which had a low battery. After replacement it was just fine.

[coromonadalix]

The de5000  is a 2 chip  lcr implementation,   same as a few models like uni-t and mastech .... no calibration software were found or was leaked, maybe an hidden button / function mode ??

And  the input protection is limited, almost non existent ...

[MaxFrister]

Fixed!

Input divider network was bad.

R33, a tiny 0603 100 ohm resistor had drifted to 123 ohms.  Replaced with a 1% 0805 and readings are now within a few percent of the bridge measurements. 

Next, figure out what minimal input protection they left off that board and poplulate it.