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PGA900: Pressure sensor vs. internal temperature sensor

Wojciech Sobol
Prodigy 90 points

Part Number: PGA900

I am testing the PGA900 based pressure sensor using a 100 PSI sensor. I noticed that the temperature of the internal sensor increases with the increase of applied pressure to the pressure sensor.

With 0 PSI pressure I am reading the temperature of 36.2°C and the temperature is steady over time. I was increasing slowly the pressure and until 45 PSI the temperature reading was all the time the same. At 50 PSI I could noticed the temperature increase. After 5 minutes at this pressure the temperature reached 44.7°C. Another test: I increased the pressure from 0 to 90 PSI - the temperature was going slowly up. After 5 minutes the temperature is 42.8°C and after 30 minutes  44.7°C. Later on the temperature stabilize at 45.2 to 45.4°C. With the increase of temperature the readings of the ADC were going down (at 39.8°C the reading was 6932084 and at 44.7°C the reading was 69241520, 7932 less). The input pressure was constant (pressure calibrator).

After I realized the pressure (to 0 PSI) the temperature of the internal sensor was going down and after 15 minutes reached 37.1°C.

Why the temperature depends on the applied pressure? Is any reason to measure the temperature? 

  • 0
    TI__Mastermind 31655 points
    Hello,

    Could you please provide some more detail about your setup? Are you using current or voltage output mode? And what blocks are enabled in your firmware?

    I may have to do some tests in the lab to look into this. In which case I should be able to provide a response by the end of next week. In the meantime, please send me some more setup information and I may be able to respond sooner.

    Regards,
  • 0 in reply to Scott Cummins
    Prodigy 90 points

    I am usinf the pressure bridge sensor (100 PSI) and I am working in Voltage output mode. 

    Here is the configuration of all PGA900 blocks:

    M0_ConfigClock(CLK_1MHZ); 

    CONFIG_ALPWR(POWER_UP_PT_PGA_FD | ADC_EN_VREF | GATE_CTRL_SD_DISABLE);
    DAC_Config(DAC_ENABLE, DAC_RATIOMETRIC_MODE_DISABLE,DAC_GAIN_4V | DACCAP_EN);
    AMUX_CONFIG( TEST_MUX_P_EN | TEST_MUX_T_EN | TEST_MUX_DAC_EN);
    AFE_CFG_CONFIG(PGAIN_CLOSE);
    ADC_Pchannel_Config(ADC_ENABLE |ADC_ENABLE_24BIT|ADC_DECI_RATE_128US | ADC_INT_RATE_EVERY_4_SAMPLE,P_GAIN_50);
    ADC_Tchannel_Config(ADC_ENABLE | ADC_DECI_RATE_128US | ADC_ENABLE_24BIT | ADC_INT_RATE_EVERY_4_SAMPLE, T_GAIN_5_V_V);
    TEMP_MUX_CONFIG(ITEMP_CTRL_OFF | VTEMP_INT);
    ADC_Config(ADC_CFG_1_ADC_ENABLE); 
    BRDG_CTRL_CONFIG(BRDG_EN | VBRDG_CTRL_2_0V);
    UART_Config(0x00,12);
    UART_ENABLE();
    UART_RX_INT_ENABLE();
    SYST_Config(SYSTICK_RELOAD_CNT, ST_CLKSOURCE | ST_TICKINT | ST_ENABLE);

    I observed the temperature increase in every test, not once.

    Regards,

  • 0 in reply to Wojciech Sobol
    Prodigy 90 points

    Problem solved:

    I programmed another PGA900. First I tested the pressure sensor in the socket. After applying the pressure of 90PSI the internal temperature and the pressure reading were constant. Next I soldered the same PGA900 on the PCB. Now after applying the same high pressure the internal temperature and pressure readings were going up.

    Finally the PGA900 chip is working fine. On the other side of the PCB there was a relay and his driving transistor. The relay was switched ON at 50 PSI. The overheat was caused by the temperature rise of the transistor.