SMART TUNER SMT6 - CALIBRATION FOR THE AMP SENSOR

Perfect Power Application Notes.

 

Application Note : AN 3.13

Introduction

  • Most AMP sensors have an analog range between 0-5V
  • You can calibrate the SMT6 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.

 

 SMT6 Piggy-Back Unit - Map Sensor Wiring

 

 

Voltage

I will try not to get too technical in this next bit, but like I mentioned before the SMT6 reads this sensor over a range of 0-5V, this range is split up by the processor into segments, like pieces of a pie, of 256 steps. If this is confusing all you really need to know is that one volt represents 51.2 steps. So in the example above we have set the bottom point of the graph to display 0.2 (bar) at a voltage of 0.2V multiplied by 51.2 = 10.2.
I will explain what this means now.
AL or AH <Grid position> <display value> <voltage * 51.2>

A : refers to Absolute Manifold Pressure (AMP).

L or H : refers to the Low and High value.

Grid Position : refers to the position in the table where the bottom number is 0 and the top number is 15.

Display Value : refers to the bar value that will be displayed at that grid position.

Voltage : refers to the voltage that the AMP sensor is supplying at that point.

 

Software Calibration

To calibrate the sensor you need two points, a low value and a high value. The SMT6 use the command, AL and AH for AMP sensor. The commands with L's are the lower settings while the commands with the H's are the upper settings, a typical setting for the lower settings of an AMP sensor would be :

Set the Low Point :

 

 

SMT6 Piggy-Back Unit - Software Calibration
So in the example above for Normally Aspirated Engines we have set point 0 of the Fuel AMP graph to display 0.20 (bar) at a voltage of 0.2V (multiplied by 51.2 = 10.2), the SMT6 will display the "AMP Input V" when the ignition is switched on, the software then fills in all the points between, above and below these points.

Next set the high point, the same rules apply :

 

SMT6 Piggy-Back Unit - Software Calibration
AH 13 0.84 68.1
So in the example above for Normally Aspirated Engines we have set point 13 (third from the top) of the Fuel AMP graph to display 0.84 (bar) at a voltage of 1.33V (multiplied by 51.2 = 68.1), the SMT6 will display the "AMP Input V" when the ignition is switched on, the software then fills in all the points between, above and below these points.

Setting the AMP Scale for a turbo application :

 

SMT6 Piggy-Back Unit - Setting the AMP Scale for a Turbo Application
AH 6 0.84 68.1
So in the example above for Turbocharged Engines we have set point 6 of the Fuel AMP graph to display 0.84 (bar) at a voltage of 1.33V (multiplied by 51.2 = 68.1), the SMT6 will display the "AMP Input V" when the ignition is switched on, the software then fills in all the points between, above and below these points. This scale now indicates for a boost pressure of up to 1 bar (1.80).
I don't know of any other method of finding these two points on an AMP sensor other than finding its data sheet and looking it up on the voltage curve, you can send this curve to our technical desk at This email address is being protected from spambots. You need JavaScript enabled to view it. if you need help setting this up.