CR10 Configuration Basics
This document provides simplified summaries of various topics, from sensor connections to power supplies. For detailed information, please visit the Campbell Scientific site.
The standard CR10X has 12 single-ended inputs or 6 differential inputs. It can measure DC voltage in the range of ±2.5 Volts. It can measure only DC voltage so resistance sensors need to be part of a Wheatstone Bridge circuit and the 4-20mA signal from a current sensors needs to routed through a 100 ohm resistor to generate a voltage.
Connecting Sensors Directly to the CR10X
A CR10X has a built-in wiring panel that allows direct connection of a certain number of sensors.
Connecting Sensors through a Multiplexer
Multiplexers allow many more sensors to be connected to the CR10. You can think of a multiplexer as an automatically switched terminal box. There is a practical limit as to the number of multiplexers that can be connected to a CR10X. For the purposes of designing a system, the limit is 6 multiplexers per CR10X.
You may have either the AM416 or the newer AM16/32 multiplexer. Functionally, the difference between them is small. The AM416 switches 4 wires at one time. The AM16/32 can switch either 4 or 2 wires at one time. This means we can connect 16 sensors with 4 wires or 32 sensors with 2 wires. Most of our applications use the 4-wire mode.
For more information and wiring diagrams, see:
Powering the CR10X
The CR10X requires a nominal 12 Volts DC power supply. This is always taken from a battery, which must be kept charged. This section discusses battery charging.
Campbell supply a PS12LA for this purpose (PS = Power Supply, 12 = 12 Volt, LA = Lead Acid Battery). The main advantage of the PS12LA is the onboard charging / regulator circuit. We typically supply a mains AC charger that connects to the PS12LA to maintain charge to the battery. We can also attach a solar panel to the PS12LA. If use a solar panel, we must be sure that it will put more energy into the battery than is being used by the CR10X system.
Calculating a Power Profile
Battery capacities are listed in Amp hours, so we need this current draw converted from mA seconds to Amp hours. Dividing 6130mAs by 3600 (seconds in an hour) gives us 1.7 mA per hour or 0.0017 Amps. The lead acid battery has a capacity of 7.5Ahr's so the battery will last, 7.5Ahr / 0.0017A. This is equivalent to 4411 hours or nearly 184 days.
If we choose to maintain charge using a solar panel, the battery must have enough capacity to power the system during periods of low light. If the system is at 40° North, the reserve time is recommended as 336 hours. As we have already calculated, the battery will give us a life of 4411 hours so this is well in excess of the recommended reserve.
To decide the best solar panel for the job we must calculate the systems average daily current requirement: 0.0017A x 24Hr/day = 0.041Ahr/day. Assuming the solar panel sources current for 5 hours per day, the panel must produce: (0.041Ahr/day x 1.2) /5hr = 0.0098Amps (1.2 is the solar panel system loss). Because the MSX10's current peak is 0.59Amps, it can be assumed that the panel will provide sufficient current for the system.
For more detail on calculating a power profile, refer to the Application Note POW-SUP.PDF on the Campbell resource CD.
Communicating with the CR10X
Direct Communications (RS232 Serial): Using an SC32A or the new SC32B interface you can communicate with the CR10X via you PC serial port. The CR10X does not have a built-in serial port, hence the requirement for the SC32A/B interface. The obvious disadvantage of this method is that you have to be within touching distance of the CR10X to communicate. For remote applications this may not be practicable.
Telephone Modem: The most popular for of telecommunications for the CR10X. Using a Campbell telephone modem (COM200), the CR10X connects to a standard telephone line. Advantages are that it is simple integration process (plug phone line into modem). Disadvantages are cost. It may be expensive or even impossible to provide a phone line to the CR10X in remote or difficult access locations (tunnels, etc.).
Narrow Band UHF and VHF Radio Modems: Narrow-band UHF and VHF systems require an FCC license. The license is site only and is not easily transferable to a different site. One major advantage is that you are almost guaranteed interference free communications. Having the license protects you from someone else using the frequency./p>
Spread Spectrum Radio Modems: This technology does not require a license. It can be used anywhere. The disadvantage is that someone else may be using the same frequency. Spread Spectrum overcomes this by hopping up and down a spread of frequencies transmitting data; the theory being that data will get through one way or another. The technology is generally less expensive that UHF/VHF.
Cellular Modem: Newer cell modems and cell networks work with IP addresses. The allows "long-distance calls" between Loggernet software and the datalogger to be placed via the internet. Cell modems are power hungry. To conserve power thes CR10X controls when and how long the model is activated. This could be 10 minutes at the top of the hour or 30 minutes twice a day. In low signal areas it may be very problematic to establish communications. III- Maximum connection speed is 1200 baud (very slow).
CDPD (Cellular Digital Packet Data): This relatively new system uses a digital cellular system. It is not assigned a telephone number but rather an IP address. This means that any computer with LoggerNet and internet access can collect data. There are no long distance phone charges and communication can be from anywhere in the world. CDPD coverage is still small in the US but growing every year.
LoggerNet or PC208W: LoggerNet software (previous versions known as PC208W) is used to write monitoring programs, sending the program to the CR10, retrieving data from the CR10, etc. Slope Indicator can write logger programs to customer specifications.
Atlas Web-Based Monitoring: Atlas automatically processes readings, checks for alarms, displays graphs, and generates reports. Since Atlas works on the internet, users can access data and graphs anywhere with just their web browsers. More about Atlas...
GraphX: GraphX is used to process data files that LoggerNet generates. It can only process data from 1 logger at a time so if simultaneous data processing from more than 1 logger is required then you need to use MultiMon. GraphX cannot process data in real-time, it can only post-process data.
MultiMon: This program has largely been replaced by Atlas. MultiMon can process data from up to 20 separate loggers at the same time. It can also process data in near real-time and automatically display data on screen. It has an alarm function that warns the user should an instrument exceed alarm thresholds.
Definitions and Terminology
- Signal Conditioned EL Sensors (IPI, MonoPod)
- RTD or Thermistors (Temperature)
- 4 - 20mA Pressure Sensor
Single Ended Inputs
A single ended input measures the voltage difference of a single conductor
relative to ground.
A differential input measure the voltage difference between two conductors. The advantage of a differential sensor is that the resolution is twice as good as a single ended sensor. The disadvantage is that you can only measure 6 inputs. An example of a differential sensor could be an IPI or MonoPod EL sensor, or a load cell.
Wheatstone Bridge Circuit
Full Bridge: With a full bridge circuit 3 of the 4 resistors
are fixed and the 4 is the sensor. When all 4 resistors are equal the voltage
across the bridge is zero. A full bridge sensor is typically a differential
input. An example of a full bridge sensor could be a load cell.
4-20mA Sensor Circuit
The CR10X cannot measure current directly so the circuit below causes the
current to flow through a 100O resistor. Using Ohms Law a voltage will be generated
across the resistor.