I documented the repair of two Tektronix DM 5010 digital voltmeters here.

I will not rehash the entire calibration process here. That is easily found in the manual for the DM 5010 which is available on the Tek Wiki. Rather, I will highlight items which may help readers avoid pitfalls and save time.

Equipment Needed:

• DC Voltage Standard 190 mV DC to 1000 V DC
• Ohms standard 190 Ω to 9 MΩ
• AC voltage standard 200 mV AC to 700 V AC at 200 Hz
• AC voltage standard 1.9 V AC to 190 V AC at 20 kHz

I have deliberately not said anything about the accuracy of the standards because it is required that they be adequate for the equipment being calibrated. In my case, I am using a calibrated HP 3458A to measure the various voltages and resistance values as they are applied.

For sources I am using a Systron-Donner M107 (DC), a Valhalla 2703 (AC), and an HP 3245A Option 2 (DC and AC). In order to obtain the 190 V AC at 20 kHz, I used my HP 3245A outputting about 63.5 V rms. This fed into a shop made 1:3 toroidal transformer having a usable flat frequency response of about 8 kHz to 100 kHz. The 3245A can easily drive the output to 190 V AC at 20 kHz.

The resistance standard I used was the esi DB 877. which is a 12 MΩ standard with 0.1 Ω resolution. The long term accuracy of this standard is 0.03%, but I can get as accurate as needed by using my 3458A

Calibration Notes

Make certain that you have the memory battery problem solved before you start the calibration process. Please see my other post for details.

Before starting the calibration process, print out Figure 10.2 in the manual. This gives the location of the AC frequency compensation adjustment points. Take a bit of time to locate them, and find suitable insulated adjustment tools (don’t use a metal screwdriver please) that fit the adjustment capacitors and variable resistors. This applies to Step 5 and Step 7 in the calibration procedure.

It is possible to do only one section DC/AC/Ohms of the procedure if needed. For example, I needed to re-zero the ohms constants after finishing the entire procedure. Move the internal jumper to calibrate position, the single calibration, move the jumper back to run position.

I used coaxial cable (LMR-195) for the AC and DC voltage values < 2 V; I found this to have the least noise pickup and the most stable voltages.

I used shielded twisted pair with ground at both the meter and the resistance standard for values 190 kΩ or larger. Again this gave the most stable values with the least noise.

I used the high resolution of the DB 877 to “dial in” the required resistance values for the ohms calibration.

The ohms calibration values must be entered as numbers with trailing zeroes, so 1.9 MΩ would be entered as 1,9,0,0,0,0,0. The display annunciators will change from kilo to mega as you enter large values.

If you encounter and error “232” at any time, you have entered a value outside the range that the meter anticipates. Re-enter the value (see above).

As you go through the ohms calibration clear any error “318” before entering a zero (offset) or calibration value. (Press “clear” then proceed)

David Beard has a video about calibrating the DM 5010

I am quite pleased with the operation of the DM 5010 after repair and calibration.