Interfacing the eosGP with a CR1000 logger: Part 2

This is the second and final part of this series. Here is Part 1.

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Differential Mode

If serial mode is unavailable, the eosGP’s analog outputs can be connected to the CR1000’s differential inputs. Remove the serial extension cable from the power & data cable and replace it with the included ground connector. This supplies a separate ground reference for each analog output. The analog/ground pairs can then be connected to high/low (H/L) differential input pairs on the CR1000 as shown in Figure 2. The power can remain connected to 12 V output of the CR1000 or can use a separate supply.

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Figure 2: Connecting the eosGP to a CR1000 in differential mode [click for larger image]

This setup can be configured using Campbell’s Short Cut program as there is no complicated programming involved. In the sensor section, select “Differential Voltage” and add 3 sensors. Adjust the properties for each sensors as per Table 1 if you have a standard dual-range eosGP (5000 ppm and 20000 ppm).

 

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Figure 3: Short Cut differential set-up [click for larger image]

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Figure 4: Short Cut properties box for differential mode [click for larger image]

Single-ended Mode

If serial and differential mode are unavailable (perhaps due to lack of unused inputs) the eosGP can be connected in single-ended mode, however this is the least accurate mode and should only be used when there are no other options. Because the eosGP draws large but short-duration current pulses to power its NDIR sensor, a varying amount of voltage is dropped across the ground lead of the cable (an effect that gets worse with longer cables). This time-varying noise signal can be diminished by moving the eosGP power connector to an isolated power supply (i.e. separate from the CR1000’s supply with no common ground connection) as shown in Figure 5. The configuration in Short Cut uses “Single-Ended Voltage” as the sensor type, but all other settings are the same as for differential mode (Table 1).

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Figure 5: Connecting an eosGP to a CR1000 in single-ended mode [click for larger image]

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Figure 6: Short Cut single-ended set up [click for larger image]

Conclusion

Whether you choose to use the serial, differential or single-ended mode to set up your eosGP with the Campbell Scientific CR1000 data logger, set up should be straight forward to get up and running. Any further questions can be directed to our support team.

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