Product: VOTEM interface board
From: Down East Computers, P.O.
Box 3096, Greenville, NC
27834.
Price: $39.95 Kit
$59.95 Assembled & Tested
VOTEM stands for voltage and temperature, and that’s what this new interface from Down East Computers is all about. It comes with all the necessary components to measure temperatures with a resolution of 0.04 degrees C and voltages with a resolution of 50 microvolts.
I assembled the kit version in about 2 hours. Despite a few confusing moments, the instructions were very good. When you’re all finished, you have something you can really admire: the board is slickly sandwiched between two flat black panels for a very professional look.
VOTEM measures analog signals (voltage and temperature) by converting them into a frequency, and then measuring the frequency using a machine language program. This technique makes the hardware inexpensive and the sampling speed slow, so this interface is not suited to applications where speed is important. Calibration is done entirely in software, which leads me to be wary of very high precision applications.
The software (in the form of listings) that accompanies the VOTEM is enough to get you started and working on your own, but don’t expect it to turn your ZX/TS computer into a multimeter. The manual describes how to set up the interface to measure larger voltages (the stock interface measures between 0 and 1 volt), a resistance thermometer probe (more accurate than the stock probe), a game paddle, and a light detector.
As a convenience, the VOTEM includes facilities to route the cassette output through the on-board comparator, which cleans up the signal and can read tapes not otherwise readable. In addition, an earphone jack is provided to monitor the loading process, and an LED blinks to the program. (Hint: Remove capacitor C2 and replace it with a short. This will make the LED brighter, but it disables protection against plugging the power into the VOTEM output jack.)
I have only two complaints. First, VOTEM’s jack arrangement is inconvenient, forcing me to route wires awkwardly. Second, the unit radiates a fair amount of interference, which can make your television picture unviewable if it is already bad. If you do not already have interference, the VOTEM should not cause problems.
Down East has brought a good idea into the marketplace: for low-speed, high-precision, single channel analog to digital conversion the VOTEM is a bargain.