Test Jig Current Measurement modules - Page 1
Forum section: electronics / projects

author: hcglitte
author_rank: Regular Contributor
timestamp: March 28, 2016, 12:49:49 pm
content: Hi,I am looking for a ready made PCB module which can measure current consumption of our device under test (DUT).The DUT PCB is placed in a jig. Different test programs will be executed for which different current consumption levels will be verified.This will vary from some nA up to about 1 amps (i.e. sleep mode and RF PA on).The DUT will be controlled by a host platform which basically is a design kit from our MCU manufacturer. Hence, the external current measurement module willbe directly controlled by this design kit via SPI or similar.The current measurement PCB must be able to allow its current ranges to be selected from this kit via an interface (i.e. SPI or simple logic binary interface).So, the kit will set the applicable current range right before the corresponding DUT current test.Does anyone know of such a current measurement module or another suitable measurement approach?I know there are some modules out there with SPI which can handle single measurement ranges. One approach could be to parallell them with series MOSFET switches controlled by the KIT to select the appropriate range.Regards,HC

author: voltsandjolts
author_rank: Unknown
timestamp: March 28, 2016, 01:25:00 pm
content: Why not just use a decent 6.5 digit bench meter that you can control/query over the remote interface?

author: hcglitte
author_rank: Regular Contributor
timestamp: March 28, 2016, 01:34:30 pm
content: QuoteGood solution. But these are expensive to my knowledge (more than 500 USD (?) ). And, for a relatively small test bench I would like it not to be dependent on "bulky" and costly external devices. So, a simple small current sense module would in my opinion be a better solution.But please let me know if you have any recommendation for such a bench meter which has an affordable price.Regards,HC

author: hcglitte
author_rank: Regular Contributor
timestamp: March 28, 2016, 11:27:20 pm
content: You are absolutely right. I also have to correct myself, I meant 1uA to some amps. However, I would think that there is a market for such a simple current sensor, low cost type. A design based on the uCurrent op-amps (without virtual ground for "one way" high side current measurement only) with PMOS switching for the 10R (very low RDS-on) and 10k shunt resistors and 12 bit ADC could be a low cost solution. Optionally, the 12bit ADC could be left out as most MCU's already have this (on the test host, i.e. kit). Auto range would not be needed for a test setup as the host knows which ranges to expect in advance to the specific test program. A selling price at 100 USD would make an OK profit.

author: voltsandjolts
author_rank: Unknown
timestamp: March 29, 2016, 08:17:04 am
content: What test equipment do you have?Some cheaper handheld DMMs come supplied with USB interface cable (e.g. Tenma 72-7730A)Related thread:https://www.eevblog.com/forum/testgear/measuring-current-on-a-low-power-iot-device/

author: Apollyon25_
author_rank: Regular Contributor
timestamp: April 01, 2016, 02:47:25 am
content: If it is for your product's production line, buy off the shelf test gear, with minimal custom interfacing.If it is for overseas production line testing - definitely buy off the shelf test gear.Most have USB/RS232/GPIB interfaces.If it is for a product you think is worth designing, then obviously you'll have to design it.uCurrent is an excellent and very straightforward starting point. You could automate the shunt selection with a couple of relays/analog switches and an I2C GPIO expander.Do you want to measure steady state DC?If you need HF AC or waveform capture, you run into gain/bandwidth, and sampling rate/resolution issues.

author: mazurov
author_rank: Frequent Contributor
timestamp: April 01, 2016, 06:06:57 pm
content: You can cover your range with two INA226 chips, less than 4 bucks each in small quantities. It is a 15 bit plus sign diff.meter with 2.5uV/LSB and i2c output. One with a sense resistor of 0.25 Ohm or larger will give you microamps, another, with lower value sense resistor will cover high range. You can also use one meter and switch (or parallel) sense resistors.