Model HMP45C Temperature and Relative Humidity Probe
CR1000 Program that Computes Vapor Pressure and Saturation Vapor Pressure
'CR1000 program that calculates Vapor Pressure
Public AirTC
Public RH
Public RH_Frac, e_Sat, e_kPa
DataTable(Temp_RH,True,-1)
DataInterval(0,60,Min,0)
Average(1,AirTC,IEEE4,0)
Sample(1,RH,IEEE4)
Sample(1,e_kPa,IEEE4)
EndTable
BeginProg
Scan(1,Sec,1,0)
'HMP45C Temperature & Relative Humidity Sensor measurements AirTC and RH:
Portset (1,1)
Delay(0,150,mSec)
VoltSE(AirTC,1,mV2500,2,0,0,_60Hz,0.1,-40.0)
VoltSE(RH,1,mV2500,1,0,0,_60Hz,0.1,0)
Portset (1,0)
If RH>100 And RH<108 Then RH=100
'Calculate Vapor Pressure
'Convert RH percent to RH Fraction
RH_Frac = RH * 0.01
'Calculate Saturation Vapor Pressure
SatVP(e_Sat, AirTC)
'Compute Vapor Pressure, RH must be a fraction
e_kPa = e_Sat * RH_Frac
CallTable(Temp_RH)
NextScan
EndProg
CR10(X) Program that Computes Vapor Pressure and Saturation Vapor Pressure
;Turn the HMP45C on.
;
01: Do (P86)
1: 41 Set Port 1 High ;Orange wire (C1)
;Pause 150 mSec before making measurements so the
;probe can stabilize on true readings.
;
02: Excitation with Delay (P22)
1: 1 Ex Channel
2: 0 Delay W/Ex (units = 0.01 sec)
3: 15 Delay After Ex (units = 0.01 sec)
4: 0 mV Excitation
;Measure the HMP45C temperature.
;
03: Volt (SE) (P1)
1: 1 Reps
2: 5 2500 mV Slow Range ;CR510, CR500 (2500mv); CR23X (1000 mV);
21X, CR7 (5000 mV)
3: 3 SE Channel ;Yellow wire (SE 3), white or purple wire (AG)
4: 1 Loc [ T_C ]
5: .1 Mult
6: -40 Offset
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