Syvecs Forums

Can anyone recommend suitable water / oil / fuel temp sensors for use with the S6?

Thanks,

Tony

Cheers Ryan.

I've ordered this:-
http://www.efi-parts.co.uk/index.php?productID=125

As you can see the calibration it gives is temp vs resistance. What's the best way of converting that to voltage?

As far as I remember this is what you are looking for:

OK, now all I need to know is what the Rterm and Rbias functions relate to!

From my searching on the net, it looks like if I connect the sensor up to a steady current supply, as I have the resistance for any given temperature from the calibration in the link, I should then be able to measure the voltage.

Does that sound about right?

Rterm - thermistor resistance
Rbias - bias resistor resistance

AFAIK bias resistor value for Syvecs is not published.

Take a look here:

Z1 - bias resistor
Z2 - thermistor

So without the bias resistor values, we're going to struggle?

Pat, is it possible to get this?

I've been chatting to some of the electronics guys at work who have said it's possible to generate a voltage table for the sensor but it requires some signal conditioning. (They mentioned current loops).

Unfortuantely this is all waaaayyy above me, but I can't believe I'm the first person to come up against the problem of wanting to connect a temperature sensor to the syvecs???

What has everyone else done?

The only way i do OEM Sensors Bud is the old school way with a test bench, thermometer/minivac and heater

Bias resistor value is quite easy to determine, at least when bias resistor value is not changing - fex. some OEM GM systems bias resistor is swithced during temperature change.

Sensor and bias resistor act as a voltage divider as per equation in earlier post. So the output voltage equals the bias voltage divided by the ratio of the sum of the combined resistances divided by the sensor resistance.

The supply voltage is 5volt or very near in most systems. So, 5volt is applied to one end of the bias resistor and the temperature sensor is connected from ground to the other end of the bias resistor. The ECU reads the voltage at the junction of the bias resistor and the temperature sensor to determine temperature sensor value.

Turning the Rs = Rb x Vb / (Vs-Vb) equation around, we will find the unknown bias resistance value in a voltage divider:

where;
Rs = Sensor resistance
Rb = Bias resistor value
Vs = Supply voltage
Vj = Voltage in sensor input pin junction
Vb = Voltage bias

Let;
Rs = 2.5 kOhm
Rb = ?
Vs= 4.95 V
Vj = 1.5 V
Vb = Vs-Vj

Rb = Rs x Vj / Vb

Rb = 2500 ohm x 1.5V/(4.95-1.5)V
Rb = 3750 / 3.45
Rb = 1087 ohm

Equation must work other way also...

Rs = Rb x Vb / (Vs-Vb)
Rs = 1087 x 3.45 / (4.95-3.45)
Rs = 3750 / 1.5
Rs = 2500 ohm