Campbell Scientific AVW200 AVW200-series Vibrating Wire Interfaces - Page 54
Wireless/One Sensor/Resistance Converted to Temperature
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AVW200-series 2-Channel Vibrating Wire Spectrum Analyzer Modules CallTable avw200 CallTable avwcard NextScan EndProg 7.1.2 Wireless/One Sensor/Resistance Converted to Temperature 'This is an example of a program used by a CR1000 and AVW206 to one Geokon 4450 VW 'displacement sensor. The sensor provides a frequency, which is converted to displacement, and 'resistance, which is converted to temperature. Polynomial Gage Factors used in this example were 'taken from the calibration sheets of the 4450 sensor. The coefficients used to convert resistance to 'temperature are from the Steinhart-Hart equation. 'The CR1000 communicates with the remote AVW206 through an RF401 radio attached to the 'logger's CS/IO port in SDC7 mode. 'The Pakbus address of the AVW206 used in this example is 15. ' Public batt_volt,Ptemp Public VWvalues(6) Public VWResults Public Psi,Temp Alias VWvalues(1) = Freq Alias VWvalues(2) = Amp Alias VWvalues(3) = Sig2Noise Alias VWvalues(4) = NoiseFreq Alias VWvalues(5) = DecayRatio Alias VWValues(6) = Therm Dim Digits Dim ZeroRding(32) 'Below are coefficients for Steinhart-Hart equation used to convert 'resistance to Temp Const A=.0014051 Const B=.0002369 Const C=.0000001019 BeginProg Scan (10,Sec,0,0) PanelTemp (PTemp,250) Battery (Batt_volt) AVW200(VWResults,ComSDC7,0,15,VWvalues(1),1,1,1,1000,2500,2,_60Hz,1,0) Digits = (Freq/1000)^2 * 1000 'Convert frequency to Digits 'Convert resistance to temp F. Temp = (1/(A + B*LN(Therm) + C*(LN(Therm))^3)-273.15)*1.8+32 46