CURS100 100 Ohm Current Shunt Terminal Input Module Revision: 7/13 C o p y r i g h t © 1 9 9 6 - 2 0 1 3 C a m p b e l l S c i e n t i f i c , I n c .
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Table of Contents PDF viewers: These page numbers refer to the printed version of this document. Use the PDF reader bookmarks tab for links to specific sections. 1. Introduction .................................................................1 2. Specifications .............................................................1 3. Measurement Concepts .............................................2 3.1 3.2 Differential Measurement ....................................................................
CURS100 100 Ohm Current Shunt Terminal Input Module 1. Introduction Terminal input modules connect directly to the datalogger’s input terminals to provide completion resistors for resistive bridge measurements, voltage dividers, and precision current shunts. The CURS100 converts a current signal (for example, 4 to 20 mA) to a voltage that is measured by the datalogger.
CURS100 100 Ohm Current Shunt Terminal Input Module Datalogger CURS100 H H Rshunt 100 Ω ± 0.01% L L or G or AG FIGURE 2-1. CURS100 schematic The CURS100 has three pins: high, low, and ground; these pins are the correct spacing to insert directly into the datalogger’s high, low, and ground terminals ( on 21X, CR23X, CR800, CR850, CR1000, CR3000, CR5000, or CR9000(X) or AG on CR10(X)). 3.
CURS100 100 Ohm Current Shunt Terminal Input Module 3.1 Differential Measurement The voltage across the completion resistor is measured with the differential voltage measurement. Use VoltDiff() for the CRBasic dataloggers (for example, CR1000, CR5000, or CR9000(X)). Use Instruction 2 for Edlog dataloggers (for example, CR10X). The differential voltage measurement measures the difference in voltage between the low and high terminals. The CURS100 connects the resistor between the high and the low terminals.
CURS100 100 Ohm Current Shunt Terminal Input Module Signal From Sensor Sensor Cable Shield Jumper Sensor Power FIGURE 3-1. CURS100 L terminal connected to a datalogger G terminal using a jumper wire. NOTE 4. Normally the L terminal on the CURS100 should be connected to a datalogger G terminal (power ground) with a jumper wire (FIGURE 3-1).
CURS100 100 Ohm Current Shunt Terminal Input Module Datalogger Transducer H Signal I L Power G +12 V FIGURE 4-1. 2-wire with datalogger power Datalogger Transducer H Signal I L Power G – + Battery FIGURE 4-2. 2-wire with external power 4.1.1 Possible Ground Loop Problems The resistor must be grounded at the datalogger to ensure that measurements are within common mode range.
CURS100 100 Ohm Current Shunt Terminal Input Module transducer and everything is fine. However, if the battery voltage drops to 11 volts, a 20 mA current will leave just 9 volts for the transducer. In this case, when the battery drops below 11 volts, the output of the transducer may be in error. Transducer H Signal 2 VDC (Max) L ≥ 9 VDC I Power – + 11 VDC (minimum) Battery FIGURE 4-3. 2-wire supply voltage 4.
CURS100 100 Ohm Current Shunt Terminal Input Module Datalogger Transducer H Signal I Ground L Power G – + Battery FIGURE 4-5. 3-wire with external power 4.3 Four-Wire Transducers A four-wire transducer has separate wires for power input and ground and for signal output and ground. The signal ground may or may not be internally tied to the power ground. Some transducers have completely isolated outputs. Datalogger Transducer Signal H I L Signal Return G Ground Power +12 V FIGURE 4-6.
CURS100 100 Ohm Current Shunt Terminal Input Module 5. Sensor and Programming Example In this example, the input voltage range, and the multiplier and offset values are calculated for a 4 to 20 mA output pressure transducer. Examples showing the differential measurement made on Channel 1 are then given for the CR1000, CR9000(X), CR10(X), and 21X dataloggers; programming for the CR800, CR850, CR3000, and CR5000 is virtually identical to the CR1000. 5.
CURS100 100 Ohm Current Shunt Terminal Input Module and at 700 psi is: V = 0.020 × 100 V = 2.0 V or 2000 mV Since the datalogger measures in mV, the multiplier (or slope) must be in units of psi/mV. Therefore, the y values have the units psi and the x values mV. The equation of a line is: (y ─ y1) = m (x ─ x1) Solve the equation for m that is the slope of the line (or multiplier). m= 700 psi − 200 psi 2000mV − 400mV = 0.3125 psi mV Now replace the known values to determine the intercept (or offset).
CURS100 100 Ohm Current Shunt Terminal Input Module BeginProg Scan (1,Sec,1,0) 'Generic 4-20 mA Input measurement Measure: VoltDiff (Measure,1,mV2500,1,True,0,_60Hz,0.0625,-25.0) CallTable (Hourly) NextScan EndProg 5.4 CR9000(X) Program Example VoltDiff(Press_psi, 1, mV5000, 5, 1, 1, 0, 0, 0.3125, 75) 5.5 CR10(X) Program Example 1: Volt (Diff) (P2) 1: 1 2: 25 3: 1 4: 1 5: 0.3125 6: 75 5.6 CR23X Program Example 1: Volt (Diff) (P2) 1: 1 2: 25 3: 1 4: 1 5: 0.
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