Precision AC current source with 1A range? - Page 1
Forum section: electronics / testgear

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: March 09, 2023, 05:53:53 pm
content: I have been looking for a precision AC current source, it seems most of them are limited to 100 mA. For example, there isHP 3245AKeithley 6221LakeShore 155SRS CS580For higher current there is only Keysight B2961, but it's not that greathttps://www.eevblog.com/forum/metrology/detailed-review-of-keysight-smupower-source-b2962a/Does anyone know of any other precision current source with a 1-3A current range? Not just a high power supply for AC power simulation, but something low noise.

author: alm
author_rank: Super Contributor
timestamp: March 09, 2023, 06:30:01 pm
content: An alternative solution could be using a power op-amp likeKepco BOPdriven from a function generator. I have used these in the past as AC current source, but not for a very high precision or low noise. They are available with a fairly wide range of voltage and current ranges.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: March 09, 2023, 06:40:51 pm
content: Yes, we have a few BOPs from a long time ago and Kepco is still making what looks like the same models. Another old model is Keithley 227 that goes to 1 A, but is also fairly noisy.

author: Zero999
author_rank: Super Contributor
timestamp: March 09, 2023, 06:42:02 pm
content: What's the frequency range? Maximum output voltage?You could use a current transformer on the output of the current source, to boost the current.

author: HighVoltage
author_rank: Super Contributor
timestamp: March 09, 2023, 06:55:53 pm
content: For that purpose I use theClarke Hess 828calibrator.If you are patient, they show up from time to time cheap.

author: alm
author_rank: Super Contributor
timestamp: March 09, 2023, 08:04:06 pm
content: The Valhalla 2500/2500E/2500EN/2500EP transconductance amplifiers also come up for reasonable prices on the used market once in a while, although I'm not sure if the topic starter is looking to buy used. These are designed with limited compliance voltage for well-behaved resistive loads, though.maxwell3e10 can you define low noise for you, and what kind of stability and accuracy you are looking for? What kind of load are you expecting to drive?

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: March 09, 2023, 11:20:59 pm
content: Yes, a calibration transconductance amplifier might be better than Kepco BOP in terms of stability and noise. I will have to look into those. I don't care about absolute accuracy but would be nice to have stability at ppm level and bandwidth of 10 kHz or more. The loads are typically a few ohm and mostly resistive.Something like Guildline 7620 looks interesting, although it's a bit too pricey to just give it a try. The spec for noise on some scales is only 30dB. Does anyone have experience with this model?

author: AVGresponding
author_rank: Super Contributor
timestamp: March 10, 2023, 06:45:11 am
content: Quote from: HighVoltage on March 09, 2023, 06:55:53 pmMe too! Mine is badged as a "RFL 828" though.

author: HighVoltage
author_rank: Super Contributor
timestamp: March 10, 2023, 09:40:54 am
content: Quote from: AVGresponding on March 10, 2023, 06:45:11 amI had no idea that the Clarke Hess was sold rebadged as a RFL 828Thanks for this info.There is one on ebay right now for US $1,425https://www.ebay.com/itm/333935224413

author: HighVoltage
author_rank: Super Contributor
timestamp: March 10, 2023, 09:45:49 am
content: Another easy way to get 1A or even much more from a lower AC current is a current amplifier.I have built a few over the years.Here is one example.

author: AVGresponding
author_rank: Super Contributor
timestamp: March 10, 2023, 10:41:15 am
content: Quote from: HighVoltage on March 10, 2023, 09:40:54 amBloody hell... mine was less than £100, shipped! Heavy bugger too...

author: wn1fju
author_rank: Frequent Contributor
timestamp: March 10, 2023, 01:12:53 pm
content: Another vote for the Valhalla 2500 series. I have mine hooked up to a Fluke DC calibrator and thus I have a current calibrator (0.01%). My 2500 will do 2A and will also do AC current (with a supplied AC voltage) up to 10 kHz.The build quality, unfortunately, seems pretty average. I've attached a picture. A few op-amps, a few precision resistors, and that's about it.I see a few currently listed on eBay, but the prices are absurd (several hundred dollars asked). I wouldn't pay more than about $75 given what is inside.

author: maxwell3e10
author_rank: Frequent Contributor
timestamp: April 02, 2023, 05:34:18 pm
content: I got this Clarke-Hess 5050 precision current source. Couldn't find any information about it, but seems to work up to about 100 kHz. I haven't checked the accuracy or output impedance yet.