Voltech DC1000 peek inside

[nexus]

Hi all,

As promised, took a peek inside the DC1000 I got on eBay. For those not familiar, the DC1000 is a specialty DC current supply meant for biasing components hooked up to an LCR meter. It allows you to make accurate LCR measurements with different DC current levels flowing through the DUT.

Voltech has a good tech article on why DC bias supplies are not trivial for LCR measurements. https://www.voltech.com/products/dc1000a-25a-dc-bias-supply/how-it-works/

Anyways, attached a few pics of the inside since I don't think any of this info is out there yet.

Not too complicated on the inside. A few detailes to note:

- nice toroidal transformer for mains input.
- main MCU is a Zilog Z8 encore
- output stage consists of a bunch of ST branded TIP42C PNP jobs, other TO-220 devices on the main heatsink are just regulators and rectifiers.

Overall, seems like a well designed and well made instrument. It certainly has some physical heft to it, and the overall feel of the instrument is solid.
As soon as I figure out how to operate the interlock I can start to make some measurements!

[nexus]

Figured out how to operate the interlock. On the DB9 "interlock IN" female connector, jump pins 5 and 6, and jump pins 2 and 9 with a 6.8K (ish) resistor.

Downloaded Voltech's DC1000 control software to test with my E4980AL meter since it is supported. Setup was pretty easy. Used an rs232-usb interface with a null modem adapter for the DC1000 and my NI GPIB-USB adapter on the LCR meter. Note that the software requires the NI VISA to run.

Picked up an inductor out of the parts bin, a bourns 2300LL-561-RC. Datasheet says the following specs:

560 µH ± 20% @ 1kHz
4.0A Idc @ 30C rise
243.6 µH @ IDC

Set up the test in the software to do a 100 point sweep from 0A to 15A, medium measurement speed, 1kHz test freq, 1Vpp test signal level. Attached pic of inductance vs DCI bias directly from program, and excel data output which includes L, R, X, Q conveniently at every step. Inductor was also getting pretty hot @ 15 amps!
Open and short compensation are handled by the Voltech software as well. I'm sure there's some secret sauce in setting up comp as the power supply is involved in that operation too. It's not just the standard open/short comp that you usually do on the meter itself.

Ran a steady state IDC test with a thermocouple hooked up. At 4.0A bias for 15 mins, inductance was about 240uH as rated, but temp was a little higher than 30C spec... was floating around 34-36C. I just taped a type K on the inductor with some thermal pad material. Not a super controlled test.

Disclaimer: I am not paid, sponsored, or affiliated with Voltech or any other equipment OEM. Everything you see here was purchased by me for my own use and all information is for educational purposes!

Cheers,
Kevin

[ace1903]

If anyone is interested how it works, seems that Voltech has patent that describes it:
https://patentimages.storage.googleapis.com/3a/12/b1/9ad449331f609f/GB2527572A.pdf
Tried to understand it but it is 21 pages.
Nice instrument and I want it but it is way to much for my hobby budget.

[nexus]

If anyone is interested how it works, seems that Voltech has patent that describes it:
https://patentimages.storage.googleapis.com/3a/12/b1/9ad449331f609f/GB2527572A.pdf
Tried to understand it but it is 21 pages.
Nice instrument and I want it but it is way to much for my hobby budget.

Nice! That patent should sum up the function in excruciating detail. Interesting to see it all laid out, should make a good bedtime read!