Tutorials > Combustion analysis

Analog setup

First please select all necessary analog channels and scale the parameters according to the sensor calibration data. The pressure sensors are usually charge pressure transducers and the only amplifier which can correctly acquire these signals is DAQP-CHARGE-B, since it can also acquire very low frequencies (or even DC pressure).

There are two basic choices - either a DC or AC input coupling. A DC coupling will also measure static pressure, which is useful when a calibration is performed. A DC coupling also features a Reset button which resets the charge to zero . Now we can apply a static pressure and calibrate the sensor.

Please note that for normal (especially long term) measurements, the AC coupling should be used. The AC coupling has a time constant from 2 to 1000 second, so the pressure signal from the engine will also be measured correctly.

Another possibility is using the calibration certificate. When we have factory calibrated sensor, we will get the certificate with stated sensitivity. Pictured below is an example of such certificate.

We enter the Unit of measurement as bar and then go to the Scaling by function tab and select the Sensitivity . We enter the sensitivity from the certificate (-17,4 in our case). Once we have entered the correct scaling, we can immediately see the scaled range and current pressures. The range can be adjusted by selecting the amplifier measurement Range. Sometimes these sensors produce high frequencies spikes which can be removed with the Lowpass filter (10 or 30 kHz) . If the signal is clean, it is recommended to set the highest filter (100 kHz) in order to see the entire dynamic range, even at high RPMs.

Analog channel setup

Angle sensor setup

There are two main sensors that are used with a combustion analyzer: angle sensors with 360 or more teeth per revolution and with a zero pulse for each revolution, or the in-car angle sensors which are basically a geartooth with some missing teeth or some double teeth (a typical example is 60-2 which would have 60 teeth except two of them are physically missing to mark the beginning of the revolution).

Sensors are usually connected to CA-CPU, which is the device that creates any number of pulses and the zero mark from the input signals. In some cases sensors are connected to the analog input, but let's continue with the instructions to see how to wire the inputs for each case.

You shouldn't set anything on the first two counter inputs, because the combustion analyzer will in most cases need those counters for internal operations. If you have any additional counters (CNT – Expansion), you can set them however you like.