XMS4 - CALIBRATION OF AMP & TEMPERATURE

SENSORS APPLICATION

Perfect Power Application Notes.

 
Application Note - AN 13

Calibration of AMP and Temperature Sensors

The principles in this application note hold true in both the SMT and XMS4 range of products. The XMS4 and the SMT units are all about sensor readings, if you have the correct signal it does not matter where it comes from the unit will read it. We can claim that these units are compatible with such a wide range of sensors for two reasons :
  1. Most sensors have an analog range between 0-5V, with exception of the frequency-based signals.
  2. In both units we can calibrate the software to read a portion of the 0-5V range, it makes better sense to adjust the sensor range to read between 2-3V if the sensor being used only moves between 2-3V.

 

It is the ability to calibrate the curves that gives it flexibility but we have found that it is also a bit difficult to understand, hence this application note.

 

Diagrams

The following diagrams show the installation of Perfect Power temperature and airflow sensors, diagrams for other types of sensors can be found in the PRS development manual.

 

XMS4 Stand Alone Unit - AMP/MAP Sensor Wiring

AMP (MAP) SENSOR

 

XMS4 Stand Alone Unit - Engine & Air Temperature Sensors

ENGINE AND AIR TEMP SENSORS

 

 

Software Calibration

Temperature sensors can be calibrated to measure degrees Celsius or Fahrenheit, you could even get them to read peanuts if you want, what you will understand at the end of this application note is that it is the voltage that is important; the number on the display is just a number. The same is true for the amp sensor.

 

 

Calibration

To calibrate the sensor using this method you need two points, a low value and a high value. Both unit ranges, that is to say all the units that connect to the LetRipp software, use the same method to calibrate the sensors.

Manifold Pressure Calibration

 

XMS4 Stand Alone Unit - ShiftF4 - AMP Calibration
Normally Aspirated Calibration 0-1bar

To calibrate the software you need two points, a low voltage and a high voltage. With the Ignition on and the XMS4 powered up the sensor will generate an input voltage. This example unit is being setup at an altitude of 1600 meters above sea level. For the example above we have used the Perfect Power 2.5 bar sensor and at the current atmospheric pressure it has generated 1.53 volts. This "voltage" is entered into the "High Calibration Volts". The "position" must not be 24 because this is being setup at altitude and not at the coast where the XMS4 might find itself one day. At the coast the pressure will increase to 1 bar and the voltage will increase accordingly. For this reason the "position" chosen is 21 and the "bar" is set at 0.84 so that at the coast the sensor can read up to position 24. The "lower calibration volts" can be guessed and fine tuned once you have taken the engine to maximum vacuum and recorded the voltage of the map sensor. You can start with a voltage of 0.2 at position 1 with a BAR value of 0.20.

 

Note : 1 bar map sensors usually have a voltage of ±4-5 volts at atmospheric pressure.

 

 
Forced Induction Calibration above 1 bar

To calibrate the software you need two points, a low voltage and a high voltage. With the Ignition on and the XMS4 powered up the sensor will generate a voltage. This voltage represents the atmospheric pressure. For the example above we have used the Perfect Power 2.5 bar sensor and at the current atmospheric pressure it has generated 1.53 volts. This voltage is entered into the High Calibration "Volts" The "position" must not be 24 because this is being setup for pressures above the atmospheric pressure (BOOST). For this reason the "position" chosen is 8 and the "bar" is set to 0.84. The software will calculate the value for position 24 automatically; once you have gone to your desired highest boost and recorded the map sensor voltage for that boost you can then fine-tune the high calibration setting. The "lower calibration volts" can be guessed and fine tuned once you have taken the engine to maximum vacuum and recorded the voltage of the map sensor. You can start with a voltage of 0.2 at position 1 with a BAR value of 0.20.

 

Note : 2.5 bar map sensors usually have a voltage of 4.8 volts at 1.5 bar boost. We don't work with negatives to represent vacuum so at 1.5 bar boost we display 2.5 bar. The boost is added to the atmospheric pressure.

 

 

Engine & Air Temperature Calibration

 

 

XMS4 Stand Alone Unit - ShiftF5 - Engine Temperature Calibration

 

 

NTC (negative temperature coefficient) sensors can only be used. These sensors have a high voltage when cold and a low voltage when hot. The LetRipp software will not accept a higher voltage in the High calibration than in the low calibration. To setup the high calibration place the engine temperature sensor in boiling water (±100°C) and measure the voltage the sensor generates. It should be a low voltage between 0-1.5 Volts. Take this voltage and type it into the High Calibration Volts. Assuming the engine will get hotter than 100°C, enter 100 at position 22.

 

The Low calibration can be set for room temperature. Measure the voltage from the temperature sensor at room temperature and put that voltage into the Low calibration Volts. The voltage for room temp can vary from ±3 - 4.3 Volts. Depending on where the car will live the rest of its life the engine temp could be exposed to temperatures lower than the measured room temp. Normally position 5 is recommended for room temp calibration but you can choose any position to suit your climate.

 

 

Conclusion

Windows software should be coming out with a graphical method of calibration that will be a lot easier to use, but because of the dos recognition in windows the above methods will work in windows software as well.