# Altering pressure transducer voltage signal

Hi guys i am having some troubles figuring this out and could use some help! I want to be able to alter the output signal of a pressure transducer. The pressure transducer is supplied with 5V and then depending on the pressure it sees it outputs a corresponding voltage.

What i would like to do is install a t connector on the output signal of the pressure transducer with a potentiometer so that i can decrease the signal that goes to the device reading the signal.

for example, it the sensor is reading say 50psi and is outputting 2.5 volts but i want the device reading that signal to only see say 1.5 volts under certain conditions how would i go about doing this? If someone could draw a quick schematic or a link to one that would be great! I have tried playing around with pots on a breadboard and am getting nowhere fast!

Thanks, mitch

Link to the datasheet. We need to know what kind of output this transducer has.

Well i would like to do this to two sensors on my truck. The first is a exhaust pressure signal which has a anolog voltage output from 0.5 to 4.75V which corresponds to a pressure of 10psi to 95psi.

The second is a fuel rail pressure sensor that has a voltage output of 0.2V to 4.75V which corresponds to 0psi and 26000psi.

I do want to monitor the true pressures that the sensors are reading but send a reduced signal to the truck's computer under certain conditions. I also would like to adjust how much the signal is altered under those conditions via a pot. Maybe i would be better of reading the signals in with the arduino and outputting a reduced analog signal from the arduino to the truck's computer.

I want the pot to be the adjustment of how much the signal is altered if that makes anysense? For example if the pot is turned all the way down, the arduino outputs the same analog voltage it read in. If the pot is turned all the way up the arduino outputs a analog voltage that is say 1V less then what it read in.

Since the arduino only has pwm outputs would i need a dac or low pass filter in order to output a true analog signal?

Thanks

Mitch

anybody have any input on this?

Thanks

Mitch

Not sure if it’s quite the same, but I have attached a voltage source accelerometer to an arduino, the accelerometer outputs 5v which I needed to reduce. To do this, I attached a capacitor and a resistor that is wired to the earth, so the signal from the voltage sent to the arduino is very low. The maximum the arduino gets is 10mV.

I’ve attached the schematic.

Thanks for the reply but unfortunately I don't think that will work. What is the best way to output a true analog voltage from an arduino to replicate a pressure sensor?

Thanks

Mitch

Would a voltage divider work?

Possibly but I want to always be able to read the true voltage that the sensor is reading then be able to variably reduce the voltage signal to the trucks computer so it sees less pressure then what there truely is

Thanks

Mitch

mitchedwards: anybody have any input on this?

Thanks

Mitch

Link to the datasheet? Without knowing anything about the device there's not much advice that can be given. In particular the output impedance of the sensor is useful, as is the input impedance of the truck's computer (OK that's going to be hard to find I know).

I am unable to find a data sheet for the sensors in my truck. Is there a way to measure the input impedance of the sensors? By impedance you are saying resistance correct? I have no clue what the computer has it is a 2012 ford f350 diesel truck

Thanks

Mitch

Yes, but its output impedance, your sensor has an output...

If its a low impedance output then it will be able to drive a 1k pot or so happily, its its high impedance you might have to use a higher value of pot....

You could try loading it with 100k, 10k, 1k, see what difference that makes to the voltage.

Here impedance is probably just resistive, but its a more general term that's normally used in signals processing.

How would you suggest I hookup the pot to the sensor?

Thanks

Mitch

Would something like this work in order to reduce the voltage that the truck computer sees?

The first pot is acting as the pressure sensor in the attached picture and the second pot is the one that i would adjust in order to reduce the signal that the truck’s computer sees.

Better to use the pot as a pot than a variable resistor, you'll get a linear response then.

Could you explain what you are saying markT?

I did some breadboard testing llastnight and posted this but apparently it didnt show up on here.

the first pot is acting as the sensor and the second pot is the one that i adjust in order to alter the sensor’s output signal. with the configuration below i was able to reduce a 3.1V signal to 3.0V which corresponds to the truck seeing 1100 psi less which is a good starting point! the other thing i noticed is that at lower higher voltages it doesnt have a big impact which is a good thing for this as i do not want to alter the signal too much when the truck is idling or when there is already upwards of 26000psi of fuel rail pressure.

What do you think about this?