' ============================================================================
' Geokon 4500 Vibrating Wire Piezometer - CR6 Direct Connection
' Model: 4500AL-70 kPa | Serial: 2528061 | Cal Date: June 30, 2025
' ============================================================================

' ----- Calibration Constants (from Geokon calibration sheet) -----
Const G = -0.01490        ' Linear Gage Factor (kPa/digit)
Const A_coef = -1.477E-08 ' Polynomial coefficient A
Const B_coef = -0.01470   ' Polynomial coefficient B
Const C_coef = 137.16     ' Polynomial coefficient C (REQUIRED!)
Const K = 0.04907         ' Thermal Factor (kPa/°C)
Const R0 = 9327           ' Factory Zero Reading (digits)
Const T0 = 20.1           ' Reference Temperature (°C)

' ----- Steinhart-Hart Thermistor Coefficients -----
Const ThermA = 1.4051E-03
Const ThermB = 2.369E-04
Const ThermC = 1.019E-07

' ----- Variable Declarations -----
Public VW(6)              ' VW measurement array (6 values with thermistor)
Public Freq_Hz As Float   ' Frequency in Hz
Public Digits As Float    ' Reading in digits (Hz²/1000) - MUST BE FLOAT!
Public Temp_C As Float    ' Temperature (°C)
Public Pressure_Lin       ' Linear pressure (kPa)
Public Pressure_Poly      ' Polynomial pressure (kPa)
Public BattV

' ----- Data Table -----
DataTable(TransducerData, True, -1)
  DataInterval(0, 5, Min, 10)
  Average(1, Pressure_Lin, FP2, False)
  Average(1, Pressure_Poly, FP2, False)
  Sample(1, Freq_Hz, FP2)
  Sample(1, Digits, IEEE4)    ' Use IEEE4 for full precision
  Sample(1, Temp_C, FP2)
  Sample(1, BattV, FP2)
EndTable

' ----- Main Program -----
BeginProg
  Scan(5, Min, 0, 0)
    ' Battery check
    Battery(BattV)
    
    ' Vibrating Wire Measurement - CR6 built-in VSPECT
    ' Wiring: VW+ to U1, VW- to U2, Therm+ to U3, Therm- to U4
    VibratingWire(VW(), 1, U1, 450, 6000, 1, 0.01, "", _60Hz, ThermA, ThermB, ThermC)
    
    ' Extract values
    Freq_Hz = VW(1)           ' Frequency in Hz
    Temp_C = VW(6)            ' Temperature in °C
    
    ' CRITICAL FIX: Convert frequency to digits with explicit float math
    ' Digits = Frequency² ÷ 1000
    Digits = (Freq_Hz * Freq_Hz) / 1000.0
    
    ' Linear Pressure: P = G × (R1 - R0) + K × (T1 - T0)
    Pressure_Lin = G * (Digits - R0) + K * (Temp_C - T0)
    
    ' Polynomial Pressure: P = A×R1² + B×R1 + C + K×(T1 - T0)
    Pressure_Poly = A_coef * (Digits * Digits) + B_coef * Digits + C_coef + K * (Temp_C - T0)
    
    CallTable(TransducerData)
  NextScan
EndProg