RE: 218 PULL UP RESISTORS

Hi Everyone

I have installed a Bosch fluid temp & pressure sensor to an engine and have the ecu +5v supply to the sensor and the signal temp and pressure wires are going to Race Tech Dash 2 display

i haven't installed any pull up resistors for these signal wires as the sensor has dedicated supply and ground pins and two signal wires. Am I right in thinking that any voltage change is done in the sensor and the voltage on the signal wires do not need a pull up on each wire.

does the Bosch sensor work in this way of do i need pull ups installed

thanks.

You need to install a pullup resistor on the temperature signal wire to your 5V reference. The temperature signal is just a NTC resistive value to ground. Matched the same calibration as most of the other Bosch Temp sensors. You would normally use a 1k pullup with that sensor.

The Pressure portion of the sensor does provide a direct voltage output, and you would NOT want to have any pull-up / pull-down resistors on that signal.

Thanks David. Much appreciated.

just one more thing.

The RT Dash 2 display has its own +5v Ref pin. As the engine harness has already been built and sheaved (oops) am I save to use the dash +5v supply for the pull up or will I get interference as the supply to the sensor itself is coming from the ECU

thanks.

You need to use the +5v and ground from the device measuring the voltage on the temperature signal if you want it to be accurate. Use something else and you might not be accurate -- Only you know how important the accuracy is in your application.