Featured Product Archive
The inventions and products featured on these pages were chosen either for their
uniqueness in the RF engineering realm, or are simply awesome (or ridiculous) enough
to warrant an appearance.
| 1 |
2 |
3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
13 |
14 |
15 |
16 |
17 |
18 |
19 |
20 |
21 |
<Previous
Next>
Vintage CompuTemp 5 Electronic Thermometer (c1987).
After decades of using various outdoor thermometers that used a bimetal coil,
mercury, or alcohol, I finally decided after the latest one failed that it was time
to get an electronic one. Not wanting a wireless type that would require batteries,
I found a vintage Springfield Aspen model thermometer on eBay that had a remote alcohol bulb connected to
the indoor display by a thin copper tube. When it arrived, I discovered that the
bulb had burst long ago, and the escaped red dye in the alcohol was evident on the
packaging. That was a real disappointment since it was not electrical, which would
be the best option. Upon inspecting some of the other same model thermometers on
eBay, it appears all of them have the same issue based on the way the outdoor glass
tube looks (solid dark red line inside the tube). I didn't bother alerting any of the other vendors. Fortunately, the
person I bought mine from issued a full refund, including shipping, with no hassle.
CompuTemp 5 Electronic Thermometer showing indoor and outdoor
temperatures.
CompuTemp 5 Electronic Thermometer rear panel thermocouple
input connectors.
 At
that point I figured maybe an electronic thermometer using remote thermocouple sensors
would be a good option, since being directly wired to the indoor display unit, no
batteries would be required. My first choice for a vintage electronic thermometer
was one of the Heathkit models, preferably unbuilt, but a pre-built version would
be acceptable. After about a week of keeping a watch out for one, none became available,
so I looked for something else. This CompuTemp 5 electronic thermometer
was offered by a few different eBay sellers. The one I selected appeared to be never
used and it had the original packaging and documentation. The protective plastic
strip was still over the LED display. That's right, this circa 1987 has an old fashion
LED, not an LCD. It comes with two thermocouples, one with a 6-foot lead wire and
another with a 30-foot lead wire. The CompuTemp 5 has a clock function, a main
and an auxiliary thermocouple input, and a minimum and maximum stored temperature
value. The display can be set to step through the time, indoor temperature, and
outdoor temperature, or any combination thereof.
I performed the simple temperature calibration, then passed the long-wire thermocouple
sensor under the lower window pane and up near the top of the wall under a covered
porch, so that the sun never comes anywhere near it. The electronics / indicator
cabinet sits on a shelf over my computer (that's a vintage Cox control line Sopwith
Camel Biplane sitting atop it).
|
Inside front view of the CompuTemp 5 electronic thermometer.
The two Motorola
UNL2003A integrated circuits (ICs) contain seven (7) Darlington transistors
for driving 7-segment LED digits. Given that there are four 7-segment digits, the
controller must switch between two digits at a fast enough rate that the flicker
cannot be detected.
left side view of the CompuTemp 5 electronic thermometer
showing calibration potentiometers.
|
Inside rear view of the CompuTemp 5 electronic thermometer.
The
Panasonic MN4066B IC is a quad analog switch that likely is used to multiplex
the LED display.
Two
National Semiconductor LM8608 2-wire temperature sensor interface ICs
service the Main and Aux thermocouple inputs.
No information could be found on the Motorola SC87188B IC,
and a schematic could not be located, either. It has to contain an
analog-to-digital converter and possibly other functionality. It may be an ASIC
(application-specific integrated circuit) designed specially for the CompuTemp 5
electronic thermometer.
|
Posted January 25, 2024
|
