Need equipment to log DC voltage for weeks, months

[Div_by_zero]

I need to log a relatively small (~3.0V) DC voltage on a PCB. I'm thinking about getting a Fluke 289 which would do the job, I think, except it's battery powered and it would die well before my test (up to a month) was over. I need to log the voltage 24 times a day. I was thinking about using a PLC, but wasn't really sure what type of input module would allow me to do this. Perhaps some other piece of plug-in standalone equipment? I have an energy logger, but it's line powered and really geared towards mains work, not this sort of thing. Please advise, thanks! Edited May 1, 2014 by Div_by_zero

[panic mode]

need more info... for something on the bench, you can use PLC (powered from outlet). just need analog input card. standard analog cards include ranges 0-5V and 0-10V. depending on PLC resolution will be 8, 10, 12 or 16bit If you need something to be used on a battery power I would consider embedded solution using microcontroller. there are tons of development kits and they are low power - can run for months on battery (or years depending on battery ). one just need to check required resolution for analog input and memory needed to store the data. 30days * 24 samples is really not much data. many development kits are very powerful (16 or 32bit core) but not always easy to get familiar with. one of simplest to get familiar with is arduino - which has 10-bit ADC, arduino due has 12bit etc: http://arduino.cc/en...gReadResolution there are tons of 16-24bit ADC if you want something that really rocks. many are available as modules: http://www.adafruit.com/products/1085

[Div_by_zero]

What I am reading is clock battery voltage on a PCB. So the battery will be its own source of voltage. I never used an analog in card in such a manner but I guess it will work?

[pfort]

Is this a button battery? If so, you should consider the impedance of your analog input. On a period of a month, it could influence your battery output.

[Div_by_zero]

It's the battery that powers the RTC. Yes, it's a "button" style battery. What I would do is pass one of the test leads through a dry-contact relay, and only close the relay once per hour just long enough to take a test reading. Edited May 6, 2014 by Div_by_zero

[panic mode]

yep, if it is a coin cell battery, analog input of a standard MCU (~10k) without conditioning circuitry will drain the battery in a month or so on its own (like CR2032 for example). fortunately it is easy to obtain higher input impedance using voltage follower for example. still no any usable data... till then any suggestion is just a guess, soooo.... try answering following 1. what is your budget ( ) 2. what is your skill / experience 3. what is the type of battery under test 4. what source of power (volts/amps) is available for powering logger 5. what is the environment (moisture, temperature, noise...) 6. what is the expected footprint/weight etc.