simple solution measuring mV
- Thread starter Efried
- Start date
CAI_Support
Senior Member
We are working with Ross on an IO board for WC32, that will have amps on all 8 analog channels with adjustable gains.
It maybe a month or two from production, pending Ross' approval.
It maybe a month or two from production, pending Ross' approval.
Efried said:
WC32 is 0-5V in, not 0-10V, so at 5V it's (approximately) 5mV.
That said, with my WebAmp board, I'm using 0-40mV full scale on WC8 boards, which is about 0.04mV/bit
I also have a heap of stand-alone 4-channel amplifier boards if that's any help?
Gain can be set from unity to about 50dB (100,000 times).
Jumpers to set inverting or non-inverting mode.
Space to put input conditioning (filtering, clamps, attenuation) if required.
Runs off DC 12-15V at a few milliamps.
CAI_Support
Senior Member
In WebControl, it is measuring DC voltage, not AC, if you want to measure AC, you will need to rectify the amplified signal.
Because diode has minimum barrel voltage, you will need to shift the amp bias slightly, so that 0V will be at least 0.7V to overcome the diode barrel voltage. Put diode behind amp between amp board and WC8 analog input.
Because diode has minimum barrel voltage, you will need to shift the amp bias slightly, so that 0V will be at least 0.7V to overcome the diode barrel voltage. Put diode behind amp between amp board and WC8 analog input.
Efried
Active Member
rossw said:WC32 is 0-5V in, not 0-10V, so at 5V it's (approximately) 5mV.
That said, with my WebAmp board, I'm using 0-40mV full scale on WC8 boards, which is about 0.04mV/bit
I also have a heap of stand-alone 4-channel amplifier boards if that's any help?
Gain can be set from unity to about 50dB (100,000 times).
Jumpers to set inverting or non-inverting mode.
Space to put input conditioning (filtering, clamps, attenuation) if required.
Runs off DC 12-15V at a few milliamps.
Hi rossw,
is your amplifier board usable for rectifying 50 Hz AC signal up to 1V ?
here is some discussion about the possible implementations: http://sound.westhost.com/appnotes/an001.htm
I found this RMS to DC OP AMP. May be you can use it: http://cds.linear.com/docs/en/datasheet/1966fb.pdf
thanks
Gerfried
Efried said:
It was not designed for that purpose and would not do it without major surgery.
(The WebAmp board does have 1 spare opamp available, and a small prototyping area which would probably provide for a single channel half-wave opamp rectifier and a capacitve smoothed output. The 4-channel amp board was designed for general DC shunts and sensors, and has no prototyping area)
Efried said:
The second chip is an interesting find. I'm happy to build some boards if there's enough demand! How many do you need?
Efried
Active Member
Ok many thanks for your info. I'm a researcher not reseller. May be metering is the biggest application. 3 phase web based meter having switching capability for less than 100€ would be a cost target. May be some colleagues can step in offering that on the market.rossw said:
Cheers
CAI_Support
Senior Member
LTC1966 is an interesting chip, could be used for measuring power usage and management.
If LTC1966 directly drives WC analog input, it is best to remove the voltage divider resistor to ground, since current drain on the LTC1966 will be significant.
Once the voltage divider resistor removed, the max input will be 3.3V over 1024, or about 3mV per bit.
If LTC1966 directly drives WC analog input, it is best to remove the voltage divider resistor to ground, since current drain on the LTC1966 will be significant.
Once the voltage divider resistor removed, the max input will be 3.3V over 1024, or about 3mV per bit.
CAI_Support
Senior Member
For WC8 this is easy to do. For WC32 it is harder, because wc32 uses resistor networks, and its traces are tiny small.
