Campbell Scientific CR10X CR10X Measurement and Control System - Page 107
To 20 Ma Sensor Using, Curs100 Terminal Input, Module
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SECTION 7. MEASUREMENT PROGRAMMING EXAMPLES ;Find Temperature and Pressure. ; 04: Paroscientific (P64) 1: 1 Loc [ Temp_us ] 2: 19 Loc [ Temp_C ] * Table 3 Subroutines 01: Beginning of Subroutine (P85) 1: 1 Subroutine 1 02: Bulk Load (P65) 1: 5.8603 F 2: -3970.3 F 3: -7114.3 F 4: 102.78 F 5: 70.294 F 6: 6.6101 F 7: -119.29 F 8: 30.884 F 9: 3 Loc [ U0 ] 03: Bulk Load (P65) 1: 0 F 2: 26.337 F 3: .85170 F 4: 21.801 F 5: 0 F 6: 0 F 7: 1 F 8: 0 F 9: 11 Loc [ D2 ] 04: End (P95) End Program INPUT LOCATION LABELS: 1 Temp_us 2 Press_us 3 U0 4 Y1 5 Y2 6 Y3 7 C1 8 C2 9 C3 10 D1 11 D2 12 T1 13 T2 14 T3 15 T4 16 T5 17 Comp_Chk 18 plce_hold 19 Temp_C 20 Press_psi 21 Signature 7.18 4 TO 20 MA SENSOR USING CURS100 TERMINAL INPUT MODULE A dew point sensor has a 4 to 20 mA output over the dew point temperature range of -40° to +70°C. The dew point sensor output may be measured by the CR10X using the CUS100 Terminal Input Module (TIM). The CUS100 uses a 100 Ω, ± 0.01 % resistor to convert the 4 to 20 mA range to 400 to 2000 mV. The millivolt range was found using the relationship V = IR, where V is voltage, I is current, and R is resistance, e.g. the voltage at -40°C is given by V = 4 mA ∗ 100 Ω = 400 mV. The dew point sensor is measured with Instruction 2 (Volt Diff). The multiplier for dew point temperature is found with the following relationship [70°C (-40°C)] / [2000 mV - 400 mV] = 0.06875°C/mV. The offset is found by taking the linear relationship °C = mV ∗ Mult + Offset and solving for the Offset. At -40°C the voltage is 400 mV, thus the Offset = -40 - [400 mV ∗ 0.06875°C/mV] = -67.5°C. CONNECTIONS The dew point sensor is measured with a differential voltage measurement on differential analog input 4. The CURS100 TIM and dew point sensor are wired to the CR10X wiring panel as shown in Figure 7.18-1. PROGRAM 01: Volt (Diff) (P2) 1: 1 Reps 2: 25 ±2500 mV 60 Hz Rejection Range 3: 4 DIFF Channel 4: 1 Loc [ Dew_Pnt_C ] 5: .06875 Mult 6: -67.5 Offset INPUT LOCATIONS 1 Dew_Pnt_C 7-23