# Campbell Scientific CR1000 FAQ

Question: How do I read VW sensors with a CR1000 datalogger?

Answer: The CR1000 cannot read VW sensors directly. You must have a vibrating wire adaptor such as the AVW200. Here are some sample programs that you can use to get started. We do not provide support for the sample programs.

Question: How do I convert RTD or thermistor readings to degrees C?

Answer: Choose a formula from the table below:

 Vibrating Wire Sensors with AVW200:  Where Ohms = reading in ohmsCoefficients for Thermistor:  A = 1.401e-3     B = 2.377e-4     C = 0.00e0     D = 9.730e-8 Formula for Thermistor:   Deg C = 1/(A+B*LN(Ohms) + C*LN(Ohms)^2 + D*LN(Ohms^3)-273.2Coefficients for RTD:    J = -23.50833439     K = 227.625007     L = -341.217356417 Formula for RTD:   Deg C = (J*((Ohms/1000)^2)) + (K*(Ohms/1000))+(L) Vibrating Wire Sensors with AVW1, AVW100, or AVW4:  Where VT = reading in voltsCoefficients for Thermistor:    A=43.089     B=-240.91     C=544.27    D=-611.59    E=378.11     F=-104.78 Formula for Thermistor:   Deg C = A*(VT^5) + B*(VT^4) + C*(VT^3) + D*(VT^2) + E*(VT) + FCoefficients for RTD:   A=-435.97     B=1904.4     C=-3442.5     D=2412.6 Formula for RTD:   Deg C = A*(VT^3) + B*(VT^2) + C*VT + D MEMS or EL SC Sensors:  Where VT = Thermistor reading in volts:Coefficients:   A=9.3219     B=-54.3038     C=131.165     D=-161.2568     E=137.7711     F=-37.7705 Formula:   Deg C = A*(VT^5) + B*(VT^4) + C*(VT^3) + D*(VT^2) + E*(VT) + F 4-20mA Sensors:  Where VT = Thermistor reading in volts:Coefficients:   A=43.089     B=-240.91     C=544.27    D=-611.59     E=378.11     F=-104.78 Formula:   Deg C = A*(VT^5) + B*(VT^4) + C*(VT^3) + D*(VT^2) + E*(VT) + F

Question: I want to place my CR1000 and my AM1632 multiplexer in different locations. How far apart can I place them?

Answer: We usually recommend that the multiplexer be placed close to the CR1000, but if you must separate them, here are some points to consider:

1. Power: The CR1000 must supply power to drive the relays on the multiplexer, so you must check for a voltage drop caused by the resistance of long cables. See the AM1632 manual for power requirements.

2. Digital Ouput and Pulse: The CR1000 sends a digital signal to reset and clock the relays. The duration and level of this signal can be degraded by long cables. See the AM1632 manual for required voltages.

3. Signal Degradation: The signal from the sensor doesn’t stop at the multiplexer. It continues, unamplified and unfiltered, through the multiplexer all the way to the CR1000. Long cable lengths are subject to RF noise from the environment and resistance from the cable.

Question: Is there a way to connect a CR1000 to my SCADA system?

Answer: There are two ways to interface a CR1000 to a SCADA system.

1. Make a hardware link via RS232 using the Modbus protocol to interface to HMI (Human Machine Interface) of the SCADA system.
2. Make a software Link using PC-OPC from Campbell. SCADA system has to be compatible with OPC (Ole for Processing Control). Use Loggernet and prefered telemetry option. Loggernet acts as server, with data in Cache. PC-OPC resides on PC and acts a client. PC-OPC goes to server cache, retreives data, then makes it available to HMI, essentiall providing a software ‘bridge’ to HMI.

Discussion of OPC on the Campbell Scientific website

Discussion of SCADA on the Campbell Scientific website