In performing hydrostatic testing of buried pipelines, the section is filled completely with water, and then pressurised and the pressure and water temperature measured very accurately. If the pressure changes, there are 2 possible reasons for this, firstly the temperature of the water may change and secondly there is a leak, which is what we are attempting to determine. The temperature is measured by placing temperature probes on the wall of the pipeline at several locations. As the pipeline is buried, these probes are constructed from a fibreglass fishing rod, with the temperature sensor mounted in the end of it, and as the section may be up to 80km long, these are approximately equi-spaced.
According to the standard by which these tests are conducted, these temperature readings must be collected at regular intervals over a minimum 24 hour period, with a typical interval of 1 hour. In the past, these have been collected by a person having to drive up to the probe usually in a 4WD over some pretty remote tracks, reading the data, and then radioing it back to the base test site. This has been a constant source of frustration, and expense over the years, as there was usually a voice comms over the radio, but no data. The areas these tests are conducted typically have no cellular phone access.
After talking with techs at sporadic intervals over the years, who kept talking about bandwidth and baud rates, I stumbled over the Basic Stamp CM8880 telephone tones project, and then the Mitel Application Notes for this chip, and thought that this may be a cheap easy solution to this hassle.
I knew next to nothing about micro-controllers, but had fiddled about with electronics in the past and could also fiddle about programming a couple of flavours of basic, so how hard could this be? Little did I know.
I had stumbled over the Basic Stamp and played about with that but then came across the SimmStick concept, with the AVR Raver project. Here was a cheaper alternative to stamps with a programming language that didn't seem too arcane.
At the same time I put together a prototype board with a LTC1298 and a CM8880 on it firstly using a BS1 and then a DT104.
Whilst coming to grips with AVR Bascom, I browsed into the SimmStik contest and found Phil Ray's Temperature project. This sounded like it was along the lines of the thing I wanted to develop, so off went an e-mail, and the start of a partnership in developing this project.
Mark Alberts from MCS Electronics has tirelessly answered dumb questions along the education process, as have others in the Bascom Users Group.
Each remote site is equipped with a UHF CB radio, battery pack, and a package of a SimmStick DT104 with a 2313 micro-controller, and a SimmStick DT202 board with a MT8880 telephone tone transceiver chip, and a LTC1298 12 bit A-D chip.
The base site is equipped with a similar UHF CB radio, and a package comprising a SIMM100 with 8535 micro-controller, a DT202 with CM8880 and a DS1307 RTC. This is mounted with a 16 key keypad and a 4 x 20 LCD. A RS232 port is also installed.
Some of the LCD display screens are shown below: