Hi,
Can anyone provide some guidance re the above please? I want to connect an ARG100 rain gauge to a C terminal on a CR300 logger. The P_SW terminal is already in use with another rain guage.
*Do I connect the resistor between the rain gauge and the C terminal, or between the gauge and the Ground terminal?
*Will any 100 k Ohm resistor suffice, or do I need a high precision one (e.g. low temperature sensitivity)?
*In the manual it says [Section 14.5.3.2] "Switch-closure measurements on C terminals require a 100 k Ohm pull-up resistor to 12 V." Is that last bit short-hand for 'for a maximum of 12 V?' - anything I need to do about this?
Any advice gratefully received.
Many thanks, Andrew
The purpose of the resistor is to bias the C port high. The expectation is that when the tipping bucket tips, the internal switch will close and pull the C port low. The high-to-low edge transition will be detected and counted. It does not need to be a precision resistor, it only needs to be a current limiting resistor that will bias the C port to a >3.3V state.
Hi Sam, that's very helpful and gives me the reassurance I need. Many thanks for your assistance.