Interfacing the eosGP with a CR1000 logger: Part 1

This is the first of a two part series covering three different ways you can set up your eosGP with a Campbell Scientific CR1000 data logger. Here is Part 2.

Download complete article in full PDF format.


Introduction

The Campbell Scientific CR1000 is a popular data logger which provides a plethora of options for connecting and recording multiple sensors. The Eosense eosGP CO2 gas probe has multiple output options. This note is provided to help you decide which connection method is right for your application and demonstrate the connection process.

Required Components

  • eosGP
  • Campbell Scientific CR1000 data logger
  • Short Cut software (CR1000)
  • SSC/SLC
  • Power Connector
  • Serial Extension Cable (serial only)
  • Ground Connector (analog only)

Serial Mode

Why would you want to use your data logger’s serial input with the Eosense CO2 gas probe? Unlike basic analog sensors such as thermistors, the eosGP uses an on-board computer to make measurements and apply calibrations to calculate a highly accurate CO2 concentration reading. For the convenience of users with basic analog-only data loggers, we supply simulated analog output signals, but for maximum resolution and noise immunity, it is always preferable to use the serial output.

Eosense-App-Note-Figure-1-Serial-Mode-CR1000

Figure 1: Connecting the eosGP to a CR1000 in serial mode

The CR1000 allows up to 4 serial inputs on its control I/O ports in addition to analog inputs, allowing synchronization between serial and analog sensor readings. Simply connect pin 2 of the eosGP’s serial extension cable to the Rx input of the CR1000’s Com port, and pin 5 to a digital ground (usually labelled ‘G’) as shown in Figure 1.
The GP can either be powered from the logger’s 12 V supply or via a separate supply. In this example, Com4 is used, but with a small change to the program, any of the 4 control I/O Com ports can be used. Using the CR1000’s dedicated RS232 port is more difficult since this connector is used to upload programs and download data from the logger and is beyond the scope of this application note.

A demonstration program is available for download, and will be shown in full in the full application note. The blue text represents a basic CR1000 program which in the case of the demo measures and records battery voltage and internal temperature, though it will obviously vary based on your specific application. The red text represents the lines of program code which are added to extract and record the CO2 concentration, high range CO2 concentration, and temperature from the eosGP.

The lines starting with “SerialOpen” and “SerialIn” contain references to “Com4”. These can be changed to “Com1”, “Com2” or “Com3” to make use of the other serial ports. The eosGP outputs a new serial reading approximately every 5 seconds. When each new serial message arrives, the concentrations and temperature are updated (“Scan” should have a frequency of less than 5 seconds). Calling the data table will store these most recent values. If the “DataTable” frequency is faster than 5 seconds, the same readings will be stored multiple times since the data is only updated every 5 seconds. While the demonstration program was developed specifically for the CR1000, the techniques are applicable to other data logger models like the CR800, CR6 and CR3000 with minor changes to the program.

 

Part Two: Differential and Single-ended Modes…