Field Notes

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Twitchell Rice: 2012-01-25 08:40:00 (DOY 25)
Author: Joe Verfaillie
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Summary: Batteries now charged by generator (off solar), reset 7700 SDM address, added corner braces to box. LGR okay - calibrated.

Twitchell
2012-01-25

I arrived about 8:40PST. It was clear, cool and sunny with little to no wind. The water level in the field is high with a little water infiltrating around the base of the tower. Duck hunters were there, somewhere. There were lots of coots near the tower.

When I arrived the LGR read
7:41PST, 31.23C, 146.82Torr, 13.079usec, 10Hz, 2.505

I changed the clock to the proper time 8:38PST. I had planned to swap the LGR because of the low pressure readings from previous visits, but it seems to have fixed itself. In slow flow mode it ran at 156.02Torr. I checked the external 2um filter and it was slightly blocked so I swapped it out. When I let the end of tubing leading to the tower fall to the ground as I swapped the filter, water gushed out. However, I think the water came from inside the insulation and not inside the tubing. There was only a couple of cm of water in the water trap that I dumped out.

With the new external filter I calibrated the LGR. The cal tank has <200psi of 3.276ppm CH4. Last calibration was Dec 20, 2011.
Pre Cal: 8:49PST, 29.61C, 156.07Torr, 13.871usec, 3.282ppm, 1Hz

The first try at calibration failed somehow ending in a value (3.317ppm) farther from the span gas. A second calibration seemed to work fine and ended up right on.

When I left the LGR read
9:56PST, 23.93C, 153.81Torr, 13.060usec, 10Hz, 2.311ppm

When I arrived the 7700 was not sending data to the CR1000. The extra load on the solar system pulled the batteries pretty low and the LI7700 dropped out a number of times. It seemed to have lost its SDM address. I was able to reset the SDM address by connecting to the 7550 box with a serial cable that came with a 7500. The 7550 seems to default to SDM 2, maybe should use that.

To solve the low solar power problem, I added an AC to 12VDC supply to charge the batteries from the generator power. When I arrived the solar charger read 12.7V, 3.8A solar, 2.3A load. With the DC supply a continuous 3.3A is supplied as long as the generator runs.

I added corner braces to the box that strengthen it and seemed to square it up a bit and helped the doors fit better.

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