I have a submersible pressure sensor that requires 5V DC for excitation and will output a 0.5V to 4.5V signal proportional to the water height. I'm using a CR1000, so I'm wondering if there is any way to get a 5V excitation signal out of the CR1000, or will I have to buy something else or make a homemade precision 5V source that could be triggered by the 2.5v excitation signal from the CR1000. Thanks.
If you don't need to turn the sensor on and off, use the 5V terminal on the CR1000. You didn't specify which pressure sensor so I don't know how much current you require. See page 46 of the CR1000 manual for the current source limitations on the datalogger power connectors.http://www.campbellsci.com/documents/manuals/cr1000.pdf
It's a Keller Levelgage (http://www.kelleramerica.com/pdf-library/pdf/Levelgage.pdf) configured for 5V supply and 3-wire connection (Vcc+, GND, +Out). I'm not sure what the current draw is for one unit, but I'm planning on having several of them connected to the CR1000 along with some other sensors, in a remote location for weeks at a time, and all powered by a battery, so I don't think I can leave the sensors powered between measurements. I'm also unsure how to connect the pressure sensor output to the CR1000. Do I just connect the +Out wire to a single-ended voltage channel, assuming I find an adequate way to provide the excitation voltage?
I checked the data sheet you sent a link for and could not see one with a 5V supply. There is one with a 3-wire connection with 5V output that requires 8-28V DC supply. Many of these sensors could be powered for the switched 12V output on the logger.
If you have some special version of the sensor that requires a regulated 5V supply you could use the 5V output on the logger with a solid state switch. The SW12V switch may be OK, but you would need to check with CS Inc to see if it is OK at 5V and what the voltage drop is to see you still get an acceptable supply voltage.
With either the standard or special sensor you would measure them as a single ended input on the 5V range.
Alternatively if you have not purchased these you could look at Campbell Scientific's range of sensors, the CS450/CS455, that are far more accurate, very low power and have easy to use digital interfaces, see:
http://www.campbellsci.com/cs450-specifications
* Last updated by: aps on 12/3/2010 @ 3:04 AM *
Thanks for the helpful info. Mine is a custom sensor that only accepts 5V supply. I have quite a few of them on hand and can't justify buying new sensors with different outputs. The CR1000 specs say that the continuous 5V supply is +-4%, which would introduce too much error to my sensor measurements. I suppose I could try logging the 5V supply and hope I can later compensate for any errors, but it would be better in the long run for me to build a separate precision 5V regulator circuit that could be triggered by the CR1000.