The following information is for the EMANT300, EMANT380
Question: My system have one EMANT300 with 5 strain gauges and I need to capture @ 50hz for each strain gauge. I am using the driver Labview, and change the Positive Input for each sensor. And the parameter "sample rate" to 2500, but the maximum frequency that it is measuring is 12.5hz for each strain gauge. How can I config my EMANT300 to have 50hz for each strain gauge?
Answer: You cannot capture 50 Hz for each strain gauge. The present firmware uses a command/response method of obtaining measurements and this will be the limiting factor. This is about 40 samples/ sec. The higher sampling rates can only be used for one channel (burst mode). Also note the resolution is the best at 10 samples/sec and degrades after that.
For multiple channel measurements there is a delay between channels.
For the delay, please note the following (assuming a sampling rate of 25Hz as an example)
1) This will be the rate the ADC samples when one channel is used.
2) When it is multiplexed with the same gain (as if all channels are strain inputs), there is a 3 clock delay between samples. 25 Hz = 40 ms delay
0ms channel 1
120ms channel 2
240ms channel 1
Question: How do I get Single channel 16 bit waveform @ 2500 samples/sec (max)
Answer: You need the Read Analog 16 bit waveform vi. You can find an example of this in the folder Application Notes\Acquire Waveform
Follow up question to Q1: If I have 5 strain gauge then 2500/5(strain gauge) => 500/3(delay) = 166 samples/sec for each strain gauge. Is that correct?
Answer: That is correct on the DAQ module. But to get the info from the module to the PC, we use a command/response
protocol. A command is sent to the DAQ module, the DAQ module then responds with the result. The communication channel uses a USB
to serial operating at 115K baud and this limits the amount of data that can be passed to and fro. We are we able to get the apparent higher transfer rate for the waveform because:
1) The result is 16 bit vs 24 bit
2) Only one command is issued and then the waveform is returned.