Hi all,
I have a bunch of watermark soil water potential sensors. These old sensors have two wires coming from the gypsum block and were original made to interface with the watermark handheld meter.
I am converting them to work with the CR1000 dataloger, but I need some help interpreting the schematic shown on the Campbell Scientific Instruction manual for the 257-L.
Can you please refer to figure 4-1 on page 4 of said manual and provide a little clarification on the schematic?
In addition to the one 1k Ohm resistor, are those four(4) 100ufd polarized capacitors? Are they four 25ufd capacitors for a total value of 100ufd?
I see all four have the "+" sign indicating polarization, but the two right hand capacitor symbols " -|(- " show polarity, but the left hand capacitor symbols look like
" -||- " to me and don't indicate polarity.
Thanks for the help
The capacitors are connected back to back. Take a look in this manual as it is clearer and the connections are the same.
http://www.campbellsci.com/documents/manuals/227.pdf
If you are using a multiplexer the capacitors are not necessary as they are there to prevent polarisation. With a multiplexer the connection back to ground is brief and temporary so there is little chance of polarisation.