Dual Channel Multimeter/Data logger

[BusyEng]

Hi all,

I am looking for a Dual channel Digital Multi-meter that can measure both DC voltage and DC current simultaneously. I would also like to log the measured date at controlled intervals (anything between 1 sample/second to 1 sample/minute). After the end of the measurement I need to send the recorded voltage and current values to PC. Is anyone aware of such a multimeter in the market? (anything other than Extech 380900 as this multi-meter has an issue with having very inaccurate sampling interval settings).

Thanks,

 

[dick_freebird]

Are you dead set against using two meters? I have
one with RS-232 capability (Radio Shack). Not too
expensive. You would have to poll them separately.

What is your input voltage range? Many available PC
data acquisition systems out there, including USB, for
not-too-expensive, some offer common-strobe sampling
if that matters to you (it might). You might be able to
use voltage dividers and get more usable range at some
cost to resolution / accuracy and so on.

 

[BusyEng]

Are you dead set against using two meters? I have
one with RS-232 capability (Radio Shack). Not too
expensive. You would have to poll them separately.

What is your input voltage range? Many available PC
data acquisition systems out there, including USB, for
not-too-expensive, some offer common-strobe sampling
if that matters to you (it might). You might be able to
use voltage dividers and get more usable range at some
cost to resolution / accuracy and so on.

1) I cannot use two separate multi-meters. The readings need to be synchronized.
2) The input range for the DC current is between 100uA and 1A. The input range for the DC voltage is between 1mV and 10V
3) I do not want to use voltage dividers.
4) I do not want to use shunt resistors for measuring the current. The Multi-meter should directly measure the current

Thanks,

 

[dick_freebird]

Well, you do know that the current measurement (in
all the meters I've taken apart) is across a shunt
resistor from the "10A" jack to the -COM jack, and
for lower ranges the same deal but range-switched,
right?

You are unlikely to find a meter that doesn't work this
way because there are no wide range autoranging
current mode ADCs.

You might find more latitude if you jettison some of
your "wants" and concentrate on the "musts".

 

[schmitt trigger]

On a previous job, we had a Fluke bench meter that would meet your requirements.

 

[D.A.(Tony)Stewart]

1) I cannot use two separate multi-meters. The readings need to be synchronized.
,

To add to your requirements, you must specify bandwidth or time duration of the sample. I can understand why you need simultaneous V, I measurements to compute power, but normally this is simply done by design of 2 S&H's which operate simultaneously while the ADC is sequential. WIthout BW reduction of the signals or decimation averaging, you can also get erroneous results ( poor SNR) by taking instantaneous readings instead of average or RMS readings over a long interval. Therefore using Successive Approximation Register (SAR) type ADC's requires averaging, but integral type ADC's might not.

Before any solutions can be considered, please answer the following;

Spectrum of current and Voltage = ?
EMI sources to deal with?
Raw Measurement interval = ?
Saved Measurement interval =?
AUto-Ranging allowed?
NIST calibration accuracy [ ppm ] for each of 4 decades for both V,I,
Did you expect 0.1% error on full range implying an accuracy spanning 7 decades without auto-ranging $$$


Tony Stewart