We wish to measure dynamic strain and earth pressure readings around a railway bridge currently under construction. Most of the instruments have been installed, but the track will not be in operation for some time. We have purchased VW300 modules to handle the dynamic readings during passage of a train, but also need to acquire static readings (hourly or less frequently) during the construction phase. These are controlled by a CR1000.
A solar panel has yet to be installed, so we want to minimise battery drain, and from studying the VW300 manual I cannot easily see a way to only acquire static readings, at the low frequencies we require at the moment.
Any advice on a program to achieve this would be welcomed,
Thanks
Harvey Skinner
Please refer to section G.2 (Appendix G) of the
CDM-VW300 manual:
http://s.campbellsci.com/documents/us/manuals/cdm-vw300.pdf
Unfortunately, to get a static reading (1x per second
or less frequently), then you must run the device with
a 20Hz scan rate (slowest possible rate).
You could change the TimeIntoInterval condition
from 1x per second to something less frequent:
"If TimeIntoInterval (0,1,Sec) Then"
could be (for example):
"If TimeIntoInterval (0,60,Min) Then"
for capturing a static reading once per hour.
But it is hard to conserve battery power when the device is running constantly during that hour.
You could use the control capability of
the CR1000 to control a relat to turn the
CDM-VW300 on and off (leave it off for most of
the hour, then automatically turn it on just
to make the one measurement). However, that would be
pretty involved.
The other way would be to use an AVW200 device (or similar
with a radio), perhaps in conjunction with an AM16/32
multiplexer. You could collect the static readings that
way until the bridge is constructed and then switch over
to the CDM-VW300.
I recommend you contact your local CSI support office for
some specific guidance on this.
Thanks for the advice, I think I will go with the option of an AVW200 and multiplexer for now, until I have established adequate charging capacity