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Problem with Honeywell ASDX Analog pressure sensor

Former Member

Dear friends

Few months ago I decide to built a multi channel pressure box, so I bought 16 Honeywell ASDX differential analog pressure sensor (Model: ASDX RRX005NDAA5). the datasheet of this type of sensor attached.

Base on datasheet, this sensor has 3 active pin, pin No.1 is for voltage supply, Pin No. 2 is Analog output and Pin No. 3 is GND.

image

I design a PCB board to mount all 16 sensors on a single board. I use a 5Vdc power supply device for PCB board, now when I TURN ON the device and there is no applied pressure on sensors (just ambient pressure), the output voltages are almost 2.47 - 2.49 Volt (I checked Pin 1 voltage for each sensors and all of them is same 5Vdc). the problems are here:

 

Problems:

1. I expect when there is no applied pressure, the output voltage be 2.5V but as i mentioned above it is a little less, what is the reason?  

2. when I applied an specific pressure (for example 300Pa) most sensors shows different voltage in their output and so it is impossible to calculate the Pressures. the datasheet said i can calculate pressure by below Eq.

 

image

 

3. by the changing of the pressure, change in output voltage of sensors are not equal. for example if I increase the Pressure 500Pa, the voltage change for one sensor is almost 1.5V but the voltage change for another sensor is 0.7V!!

I will be so appreciate if help me

Attachments:
imagehoneywell-sensing-asdx-series-analog-pressure-sensors-product sheet-008090-12-EN.pdf
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  • 0

    Dear John, Michael and Douglas

    thanks for your quick reply

     

    the below picture shows my device, sensors and board

    image

    let me answer your question one by one:

    1) are you using the correct voltage for the sensor (they do 5V and 3.3V parts)

         I use adjustable -+5 Vdc and set this power supply on 4.99V

    2) is the load > 5k

        dear Michael and Douglas, I don't use any resistance on pin 2

    3) have some been damaged - the damage pressure for a 5"H2O device is only 15" which is  a very low pressure.

        I use this sensor in a low speed wind tunnel (the MAX speed is around 45 m/s and it is equal to  1113.7 Pa), so I don't think sensors damaged

    4) Capacitor

         I use one 100nF before any Vss pin of each sensor

     

    do you think the problem may be caused for the way i connect sensor to pneumatic connector? (see below picture)

    actually I am a mechanical engineering graduate and not very familiar with electronic details, can i use a 10 Kohm resistor? and do I use this resistor on output (Pin 2)

      imageimageimageimage

  • 0 in reply to Former Member

    Hi Ashkan,

    I believe that and have solved your mystery. The minimum load of 5K would be necessary for proper operation. 10K would be outside of specifications and might not work properly just as no load does not seem to work properly. If you can't find 5K resistors to put between pin 2 and ground then perhaps the more common 4.7K will be available. Since this is a precision instrument is is probably a good idea to match the resistors or get 1% values. This may not make a big difference but it is good procedure. Keep in mind that whatever circuitry that you feed the outputs of the sensors into will also contribute to the load. Right now the only load is probably the 1 meg or so of load imposed by your meter.

    John

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  • 0 in reply to Former Member

    Hi Ashkan,

    I believe that and have solved your mystery. The minimum load of 5K would be necessary for proper operation. 10K would be outside of specifications and might not work properly just as no load does not seem to work properly. If you can't find 5K resistors to put between pin 2 and ground then perhaps the more common 4.7K will be available. Since this is a precision instrument is is probably a good idea to match the resistors or get 1% values. This may not make a big difference but it is good procedure. Keep in mind that whatever circuitry that you feed the outputs of the sensors into will also contribute to the load. Right now the only load is probably the 1 meg or so of load imposed by your meter.

    John

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