Transducer Amplifier: Benefits & Use for 0-30mV Output

[james2286]

Hi there. I currently have a system that is about to have a load cell installed. The output of the load cell with the 15V excitation voltage will be 0-30mv (2mv/V sensitivity). Now forgive me for asking, as I am not knowledgeable in this area (I have some electronics background, being a Mechatronic engineer, but there are many gaps in my knowledge), but what are the benefits of either buying, or making an amplifier? Our data acquisition card can accept analogue input voltages ranging from -10 to 10V. From reading the manual, it has its own PGIA (programmable gain instrumentation amplifier) that is supposed to dynamically adjust gain so that full resolution is still maintained in the digital conversion. Therefore, my thinking was that if the DAQ card has its own amplifier and resolution is kept intact, that perhaps an amplifier would really be needed?
However I've spoken to a few more people and I heard that you can get amplifiers that attenuates noise while amplifying only the signal? Is this true? In this case would it be beneficial to buy one, or if possible even make one?

Thanks for any help,

Jamie

 

[dlgoff]

However I've spoken to a few more people and I heard that you can get amplifiers that attenuates noise while amplifying only the signal? Is this true? In this case would it be beneficial to buy one, or if possible even make one?

What is your application? Most transducers I've worked with will provide a means to calibrate and are purchased with a output that is compatible with you acquisition system.

 

[Mike_In_Plano]

Most of the guys who are doing validation testing on a machine put load cells / strain gauges everywhere and route them to central data acquisition systems. There's a lot that can go wrong with this method. Particularly if you don't have experience bonding strain gauges and electrical noise gets into your system.

Then again, in this case, you have a lot of data to collect, so a Fluke data bucket, or an HP data acq is the way to go.

PC based data acquisition systems tend to be noisier and are more limited in range, so I don't recommend them for sensitive data acq.

For products, such as scales, the cost and performance drives you towards a dedicated solution with an amp. It's much easier to sell the end user a guaranteed stable 0-5 volt output than a hopefully functional -?/+? mV.

- Mike

 

[Bob S]

Your load cell voltage output is almost certainly a differential output, and not referenced to either ground or Vcc (+ 15 volts). So an operational amplifier set up to amplify small differential voltages with a good (high) common mode rejection ratio is essential. We need more detailed information on your specific load cell specifications.
Bob S