I have a ADC-24 logger and i'm struggling with reading pressure sensor voltages and setting up the terminal board.
i'm using the terminal board supplied with the logger.
since the +5 volts low current power supply is only up to 2 milliamperes, i need to use an external power source for the sensors since they use more current thats supplied by the logger. i can barely use one sensor with the internal supply, since the voltage drops to 3,2 volts once a single sensor is connected.
i'm using Caterpillar pressure sensors (factory installed in the machines and engines) which use 5 volts for feed and the range of outpout is from zero to 5 volts. hence the ADC-24 max channel voltage is 2500mV i need to use a voltage divider which lowers the signal voltage by half. i'm using 22 ohm 0,5 watt resistors to lower the voltage by using the principle shown in the terminal board user guide (appendix 2.1.3 page 4).
the problem i'm facing now is: once i use an external 5 volt source for the sensors, what is the correct way to connect the ground to the channels? for example: i have a sensor signal connected to the terminal board channel 1, sensor feed and ground are connected to the power source, there is no readable voltage to the channel, probably since the analogue ground is missing. then i connect a jumper from the power source ground to the terminal board analog ground, and i get signal from the sensors.
but is this the correct way to connect the analog ground when i'm usig multiple sensors and a voltage divider?
should i route a jumper for each analogue ground from the power source?
also would it be enough to use only one 22 ohm resistor for the analogue ground (since it is shared by all channels on the terminal boad), and individual resistors for the channel inputs (inline, one per channel)?