UR analog value does not change with temperature

[EmilHa]

So something strange is happening with my Lambda UR values, I have a constant signal of 860 +- 5 that does not change with temperature, even if I trick the program to heat the sensor.

Do you know what the UR output from the CJ125 is based on? Is it the reference resistor in the sensor?

[Christian_Bylund]

So something strange is happening with my Lambda UR values, I have a constant signal of 860 +- 5 that does not change with temperature, even if I trick the program to heat the sensor.

Do you know what the UR output from the CJ125 is based on? Is it the reference resistor in the sensor?

Hi, I believe the CJ125 does not output UR as an analog reference of the temperature unless it detects a PWM input on the heater gate diagnostic pin (DIAHG). And probably the diagnostic register need to be 0x28FF. Check the block diagram and you will find the multiplexers. The temperature is a function of the nernst cell resistance. Bosch is referring to a guide value for the time to activity after switching ≤ 10 s on the sensor heater. By settings the calibration mode register you will get the output at 780°C, typically 176 ADC. And as you say around 860 ADC for 20-25°C.

Are you trying to map the sensor temperature?

[EmilHa]

Hi, I believe the CJ125 does not output UR as an analog reference of the temperature unless it detects a PWM input on the heater gate diagnostic pin (DIAHG). And probably the diagnostic register need to be 0x28FF. Check the block diagram and you will find the multiplexers. The temperature is a function of the nernst cell resistance. Bosch is referring to a guide value for the time to activity after switching ≤ 10 s on the sensor heater. By settings the calibration mode register you will get the output at 780°C, typically 176 ADC. And as you say around 860 ADC for 20-25°C.

Are you trying to map the sensor temperature?

Since the Mosfet driver, which is connected both to the Heater mosfet and the CJ125_DIAGH through OUTA and OUTB respectively, the CJ125_DIAGH should have a PWM input. The diagnostic register does indeed gives me 0X28FF, and the heater is working, I can see the heating element starts to glow red. So the CJ125 thinks that the temperature is constant at 20-25 °C. (actually at 23.0 °C since we have a climate controlled lab).

I want to be able to read the actual temperature, and I want the chip to successfully control the heater. We are trying to use the sensors in a research project so we cant really just use it as is, we need to calibrate it and get a good hystersis.

How fast can you ship to sweden?

[Christian_Bylund]

Since the Mosfet driver, which is connected both to the Heater mosfet and the CJ125_DIAGH through OUTA and OUTB respectively, the CJ125_DIAGH should have a PWM input. The diagnostic register does indeed gives me 0X28FF, and the heater is working, I can see the heating element starts to glow red. So the CJ125 thinks that the temperature is constant at 20-25 °C. (actually at 23.0 °C since we have a climate controlled lab).

I want to be able to read the actual temperature, and I want the chip to successfully control the heater. We are trying to use the sensors in a research project so we cant really just use it as is, we need to calibrate it and get a good hystersis.

How fast can you ship to sweden?

So you are designing your own circuitry? I can ship to Sweden (from Sweden) so it's quite fast and you will then have a working reference to evaluate on.

[EmilHa]

So you are designing your own circuitry? I can ship to Sweden (from Sweden) so it's quite fast and you will then have a working reference to evaluate on.

No I'm using yours (lambda shield 1.0) , andsince you circuit is getting feedback from the CJ125 about the temperature I would assume I could convert the UR value to a temperature.
All I am changing is the code, at least for now.

Alright, Im guessing my unit is broken so I will have to order a new. Thanks for your help.

[Christian_Bylund]

If you send it to me I could verify the function. Preferably with sensor. It sounds like a faulty sensor.