Keithley SMU as electronic load? - Page 1
Forum section: electronics / testgear

author: dzseki
author_rank: Frequent Contributor
timestamp: August 15, 2019, 07:40:46 am
content: A question just for sainty. At work we don’t have any electronic load, but we have a few SMUs (mainly Keithley 2612) laying around. If I want to use the SMU as an electronic load the best is to set the desired source current -1x, ie. if I want to dump 1A from a circuit under test (a power supply, obviously) then I set the SMU to „Source I: -1A” is it that simple? Providing that I stay within the power specifications the Keithley.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 15, 2019, 07:49:50 am
content: I've wondered about the electronic load portion of SMUs too and how that'd work exactly. Like whether you could source and sink power with the same SMU or you'd need two units for that.

author: Yansi
author_rank: Super Contributor
timestamp: August 15, 2019, 08:29:36 am
content: As the smu (2600) is i think a 4quadrant psu, you can pf course sink and source current. However i woud be very cautious about the dissipated power inside the smu. So please consult the manual thoroughly. It is an expensive piece of kit to get damaged.

author: JxR
author_rank: Unknown
timestamp: August 15, 2019, 08:34:53 am
content: Quote from: dzseki on August 15, 2019, 07:40:46 amYes, it is that simple.

author: dzseki
author_rank: Frequent Contributor
timestamp: August 15, 2019, 08:42:26 am
content: Thank you for the answers.Basically what I want to look at the moment is to characterize some low voltage lines up to 15V, and up to 1A. The Keithley is specified for 1.5A up to 20V, so I guess I should be OK dissipationwise.

author: JxR
author_rank: Unknown
timestamp: August 15, 2019, 08:56:42 am
content: Quote from: dzseki on August 15, 2019, 08:42:26 amYou should be fine with those ranges. My 2450 will complain about internal temps if I keep it sinking 1A of current over a long period of time, but it will auto-shutoff if it becomes a problem.I'm not really familiar with the 2612 personally, but for the 2450 you can set the output to "high-z" mode which will put a relay between the inputs when the output is switched off. Maybe not a big deal if your just dealing with power supplies, but if you want to use it as a load for batteries in the future that is the mode you want to have the output on. Either way, it is an additional safety feature you may be interested in when operating as a current sink.

author: Mr. Scram
author_rank: Super Contributor
timestamp: August 15, 2019, 08:58:09 am
content: Quote from: JxR on August 15, 2019, 08:56:42 amI assume you can't sink and source with the same SMU at the same time?

author: JxR
author_rank: Unknown
timestamp: August 15, 2019, 09:03:28 am
content: Quote from: Mr. Scram on August 15, 2019, 08:58:09 amNo, it can only source/sink either current or voltage (but not both) at a time per output. There is a model or two that have more than one output though.Also, whatever your sourcing you set a maximum limit for the "measure" function. IE, when sourcing Voltage, you set a current limit. When sourcing Current, you set a voltage limit.Edit: Technically, you can do strange things like connecting two SMUs, and have SMU#1 sink current, and measure voltage. Then have a SMU#2 sink voltage and measure current. Then SMU#1 would show both negative current and negative voltage on its display. Although still, there is only a single source for each unit, regardless if it is positive or negative.

author: aronake
author_rank: Frequent Contributor
timestamp: June 06, 2024, 03:28:09 pm
content: I want to use a SMU to test some LT3045 based voltage regulators to see how they behave the more current they draw.The problem i have is as i increase current sink, the LT3045 shuts off at certain current. If I then continue to increase the current draw, the SMU will start applying a negative voltage on the output of the LT3045 to achieve the set current sink. I dont want this to happen, but the SMU behave like an electronic load i.e. lower resistance with higher current until when the LT3045 stop delivering current and the SMU turns into a short. Can this be done?

author: aronake
author_rank: Frequent Contributor
timestamp: June 06, 2024, 04:04:58 pm
content: Quote from: aronake on June 06, 2024, 03:28:09 pmI figured this out myself. I though current source mode was supposed to be used, but ofcourse not! Set the SMU to source 0 volt, and then use current limits/compliance to allow it to drain like an electronic load.

author: aronake
author_rank: Frequent Contributor
timestamp: June 07, 2024, 02:35:32 am
content: Quote from: aronake on June 06, 2024, 04:04:58 pmAnd reading this again now when I have tried things, this is what is being confirmed in 4th post in this thread.