Pit Volume Totalizer


The COSMAC wasn't just a hobbyist microprocessor; the 1802 found a niche in low power embedded systems, from satellites to this pit volume totalizer (PVT) currently in service on Alberta drilling rigs. The device monitors and displays mud tank volume, trip tank volume, return flow (mud coming out of the hole), and provides pump stroke count and rate from the main mud pumps. Serial data is transferred to a PC network, which updates a realtime database via satellite. 

Pierre Lagasse designed and built the system seen on this page, and was kind enough to provide cosmacelf.com with a few photos. About 100 of the devices are in service, and Pierre says they are “extremely reliable and stable.”


Low power? You bet: “The entire system, including lcd's, cpu, mud level probes etc. require about 30ma (max) to power and the entire electronics is intrinsically safe, good for Class I, Div 1, Gr. ABCD. -40C, of course also including LCD's.

The board includes battery backed RAM (2 pages, 4 1823s), CMOS 27512, an 1854 UART, and an assortment of support chips. It also has a 10 bit A/D converter (now obsolete), analog multiplexer, counters, latches, etc.


What about software? “The software was at first written using the RCA COSMAC DOS Development System (CDS III) CDP18S007. RCA’s CDP18S030 Micromonitor (emulator) was used also. Eventually, the software was transported into a PC via serial port and converted so that Avocet’s Avmac18 (1802) assembler was used (and still is). 

“(DOS edlin is a real Cadillac compared to the original editor used in the original RCA development system. I could tell a bunch of stories here, but probably nobody would believe them!!)” 

© Dave Ruske 2001-2022, except where noted