HP 54701a active probe power supply - Page 1
Forum section: electronics / testgear

author: dadler
author_rank: Unknown
timestamp: April 30, 2015, 09:13:07 pm
content: Hi all-I have a HP 54701A active probe, which I intend to use with a DSA815.These probes have a 7 pin proprietary power connector, which is intended to plug into the HP 1143A "probe offset control and power module". I do not have the 1143A power supply (and they cost about $400 on eBay, which is way more than I paid for this probe), so I intend to build something up to power this probe. User guide for the 1143A is here:http://literature.cdn.keysight.com/litweb/pdf/01143-97000.pdfDoes anyone have any suggestions on the best way to drive this probe? It looks like it needs +17.3 Vdc and -17.3 Vdc @ 300 mA. I'm not sure if the +/- 5ma current source (which apparently drives the offset circuitry) is optional or not (believe it is optional with zero mA = zero offset). I also don't know how clean the input voltage needs to be (the user guide shows +/- 500mV), or whether the probe has sufficient internal filtering circuitry to support a homebrew hack power supply.I would love to not hack off the proprietary connector on the probe. HP makes an extension cable which I imagine has the mating connector ("• 01143-61602, 1.5-meter (59-inch) probe power extension cable"), but I can't find a source for this cable/connector.I suppose I am asking if anyone else has done this before, and if so, how you handled powering the probe?Thanks

author: dom0
author_rank: Super Contributor
timestamp: April 30, 2015, 10:04:10 pm
content: The connector looks like a typical LEMO product. Maybe you can get Agilent part # 1252-4418 from Agisight.There's a service manual here:http://www.nscainc.com/uploads_2014/product_guides/A_1143A.pdfDoesn't give noise figures. So probably anything reasonable (<300 µV) should be ok I guess. The UC1834 datasheet doesn't even mention "noise".

author: dadler
author_rank: Unknown
timestamp: April 30, 2015, 10:45:26 pm
content: Thanks for the reference--it does look like a LEMO connector. It would be most excellent if I could find a mating connector.I looked at the (albeit modern) UC1834 datasheet, and it seems to have a fixed 1.5V output. I assume they are using this more as a regulator-reference and amplifying the output. The guide you (and I) linked mentions that they feed the output of the positive back into the negative supply to ensure the +/- outputs track together.Since I'm a newb I was hoping something like a simple circuit based on a LM317+LM337 would work, but I might be being naive (as it seems the important part of the supply is that the +/- voltages are exactly matched under load, not the absolute voltages).But I am a software engineer dabbling with electronics as a hobby--so I am probably wrong about everything.

author: dadler
author_rank: Unknown
timestamp: May 01, 2015, 02:01:53 am
content: Quote from: dom0 on April 30, 2015, 10:04:10 pmThanks again for the hint on the LEMO connectors.The connector is this exact one:http://www.mouser.com/ProductDetail/LEMO/FGG0B307CLAD52/?qs=sGAEpiMZZMvf6myxbP4FpOY1ZwMQJpdX0RTDTNTAh98%3dGeez they are expensive.Here is the panel mount female socket, which should match my probe:http://www.mouser.com/ProductDetail/LEMO/EGG0B307CLL/?qs=sGAEpiMZZMvf6myxbP4FpFBrG%252bqjJSuds2Qv6ODVy%2fc%3d

author: dadler
author_rank: Unknown
timestamp: May 21, 2015, 08:23:08 pm
content: Well, I ended up winning an eBay auction for a 1143a supply for ~$125. Unfortunately, the eBay vendor shipped me a 1142a and some other guy (who won the auction for the 1142a @$30) received my 1143a.After playing swaparoo (other guy shipped the 1143a directly me to me, I sent to him, and I just hoped it would work out?), I have a clean and working 1143a that powers my active probe perfectly. The offset control is particularly useful.I might post a tear down if anyone is interested, although I expect it to align with the service manual.Anyways, I'm glad I didn't preemptively order the LEMO connectors from Mouser!

author: Mosaic
author_rank: Regular Contributor
timestamp: June 08, 2016, 03:48:15 am
content: Can you share the pinout voltages for the probe supply so I can DIY one?Can't find any for < 250thcxAncel