I have been doing a lot of reading and website searching, but cannot find (or interpret) the information I need for this project. I am working with a pressure transducer from the early 1970's, so I need help.
I intend to connect this to the arduino, if practical, and record the pressure readings.
Pressure Transducer Info from old water level recorder:
Sensor is based on a pressure controlled quartz crystal oscillator with frequency 36-40KHz
Range: 0-200 psia
Resolution" 0.001% of full scale
Integration: 40 seconds
The total hydrostatic pressure is recorded as two ten bit words.
Conversion formula (convert raw data into engineering units): (A + a) + (B + b)N + CN^2 + dN^3
N = N1*1024 + N2
3 wires, Vin, Out, and Gnd
Other information found through various sites is that it requires a 6V input and that it, I believe, is a 4V peak-to-peak square wave output.
Is there some form of drawing or key to explain what the values in the formula refer to?
If the output is 4V peak to peak then you may need to offset the square wave if it's swinging between -2v & +2v as arduino pins don't like negative voltages. If the wave is > 5v then you would also need to offset downwards so it does not exceed 5v.
If the pressure is relative to the frequency of the square wave then you could use an interrupt pin to capture transitions and measure the time between them. It could store the last reading or do an average/running total to be accessed from the main code.
"The total hydrostatic pressure is recorded as two ten bit words."
The formula "N = N1*1024 + N2" will turn two 10-bit words (N1 and N2) into a 20-bit word (N).
"Conversion formula (convert raw data into engineering units): (A + a) + (B + b)N + CN^2 + dN^3"
Without knowing the constants A, a, B, b, C, and d this formula is useless.
Do you have any more data about the sensor? Manufacturer? Model number?
Do you have the "Aanderaa standard type Data Storage Unit 2990 or 2990E"?
Are you trying to read the ultrasonic (16.384 kHz) pulses the WLR7 uses to communicate readings to the surface? If so you probably need a spec for the PDC-4. (Pulse Duration Code 4 s.) format.
The 2 10-bit words come from the circuit, which I believe can be worked around as I am now using a microcontroller rather than the current circuit configuration...which records the information onto 1/4 inch reel to reel tape, the reason it needed to be in 2 10-bit words.
Information written on Sensor (the manufacturer wasn't able to give me much additional information):
Paroscientific Inc., Digiquartz Pressure Tansducer, Model 2200 AS-002, Range 0-200 psia
I am new to coding and everything. I am on a workterm and have been given this project to play with, they know I am a novice and thought it'd be something I could learn from.
Attached is the calibration information, which gives 4 coefficients, which should be the A, B, C and d referred to in the equation. My problem is that I am unsure how to code this properly without guidance, and could possibly figure out how to wire it up with a hint or two.
The unit I have is indeed Aanderaa, although not the WLR7...It is the WRL4, pre-data storage unit.
Thank you for any information that you guys have been giving me.
"Power Requirements ................ +5 to 16V DC at 1.3 mA Max"
That's good.
"Pressure signal is a frequency output with a 10% frequency change within the frequency band 30 KHz to 42 KHz."
"Both pressure and temperature output signals are nominally square waves of 4 volts amplitude peak to peak."
I'm guessing that is the "square wave" you want to read. I'd start by looking for frequency counter sketches.
Most Digiquartz Broadband Pressure Transducers bring out their output and power connections on flying wire leads. The pressure and temperature signals are typically brought out separately as twisted pairs with power/signal ground. The wires are color- coded per following table:
TABLE 4-1: Transducer Wire Color-Coding
Wire Color: Signal
Red: Power
Blue / Black twisted: Pressure Signal / Ground
White / Black twisted: Temperature Signal / Ground
The Pressure transducer is most likely not very different from those listed on the paroscientific site, although it only has 3 wires, no temperature sensor included, and the transducers on their site have datastorage, which mine does not.
I will go look into frequency counter sketches now. Thank you
This seems to be far over my head in understanding what it is I am supposed to do to be able to read pressure. Thank you to anyone who has had suggestions.
So far I have not seen any information on how to convert from the frequency information to the numbers. Without a way to get from frequency to numbers there is no way to do the conversion to pressure.
In the calibration document they say:
X = 1024 * (CH.1+1024) + CH.2
That only works for CH.1 values below 512. If CH.1 is above 512 they actually use the formula:
X = 1024 * CH.1 + CH.2