HP 4328A Milliohmmeter update and repair - Page 1
Forum section: electronics / testgear

author: Tomorokoshi
author_rank: Super Contributor
timestamp: July 20, 2020, 01:35:09 am
content: I got an HP 4328A Milliohmmeter for a specific technical project1.It was rather cheap on ebay, and was missing half of the Kelvin probe. This was clear from the listing, so no surprise.The update was to replace the original Kelvin probe assembly with independent banana terminals. I used Pomona 3750.The unit resistance of 12 AWG copper wire is 5.21 mohms/meter. The length of wire between the leads is 0.0762 m. Therefore, one would expect around 5.21 * 0.0762 = 0.397 mohms. This is closely matched by the meter after going through the calibration procedure in the manual.1Honest. Not just adding to the collection.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: July 20, 2020, 02:25:20 am
content: Hi,I also have one of these meters. Mine was missing the leads. I bought the connector from Digikey.The part number is RM12BPE-5PH(71) Digikey: HR1732-NDIt is made by Hirose.Regards,Jay_Diddy_B

author: Tomorokoshi
author_rank: Super Contributor
timestamp: July 20, 2020, 02:45:02 am
content: Mine was the older version, with a permanently attached cable that terminates to a connector that holds the two Kelvin leads. Basically no replacements available. At some point they changed to the updated connector version.With the Kelvin leads still on the test wire, I transferred it to my 250 mA current source on the Force leads, and measured the voltage on the Sense leads. I got 0.097 mV. Therefore, as a calibration datapoint I get 0.097 mV / 250 mA = 0.388 mOhms. I looks like I'm directly measuring around 0.393 mOhms, so compared to the other values it's doing very well.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: July 24, 2020, 12:35:11 pm
content: Today is July, 24 2020, so it's appropriate to post this picture:52 years of reliable service.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 14, 2020, 08:41:17 pm
content: Sometimes brand new parts show up for this HP 4328A,like this analog dial.Someone got lucky for US$ 23,50https://www.ebay.com/itm/383614194226

author: Tomorokoshi
author_rank: Super Contributor
timestamp: September 14, 2020, 08:49:30 pm
content: Quote from: HighVoltage on September 14, 2020, 08:41:17 pmHow did I miss that? My search was still open.Yes indeed, someone did get lucky.

author: Electro Fan
author_rank: Super Contributor
timestamp: September 14, 2020, 09:23:26 pm
content: Quote from: Tomorokoshi on July 20, 2020, 01:35:09 amsure

author: precaud
author_rank: Frequent Contributor
timestamp: September 15, 2020, 02:09:38 am
content: Quote from: Jay_Diddy_B on July 20, 2020, 02:25:20 amSame here. Nice little meter. I put a little note on mine to remind me of its 1kHz measurement frequency.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 15, 2020, 09:51:22 am
content: I just bought one very cheap but without the cable and no connector and unknown condition.

author: factory
author_rank: Super Contributor
timestamp: November 06, 2024, 08:05:57 pm
content: Quote from: Jay_Diddy_B on July 20, 2020, 02:25:20 amSeems Hirose have made this one obsolete, the replacement was ending in (76) which is also obsolete, some places may still have stock remaining.Possible replacement is ending in (81), hopefully Mouser will make it available in quantities of 1 to 5 pieces.https://www.mouser.co.uk/datasheet/2/185/RM12BPE_5PH_252881_2529_CL0109_0420_1_81_2DDrawing-3472361.pdfDavid