HeathKit Digital Weather Computer

[David Hryckiewicz]

Heathkit 4001
DIGITAL WEATHER COMPUTER
Need: Help on how to obtain or make temperature sensor's

Hi group!
              I have finished building this beautifully presented weather station which was obtained ( unfinished ) from a Hamfest here in Australia many years ago. All is working fine, except that the temperature function flashes at random,  due to the Temperature sensor's not been  connected. ( they were  missing )

The Heathkit manual states:- A301 indoor temperature sensor - 100-1728
                                         
                                           A302 outdoor temperature sensor - 100-1727

The schematic shows a 4 leg device with 3 leads going to main computer display case.

Text in the manual states that A302 is a 3-terminal device, since two pins (1 and 2) are internally conected togeather. this common connection is then connected via the 3-wire cable to chassis ground. 
Externally, pins 3 and 4 look like a 6.8-volt zenner diode. Actually, however, the voltage between pins 3 and 4 varies linearly with temperature.

I have tried to use a LM335 Precision temperature sensor in this funcion in  many different configrations with poor results.

I hope that someone in the group may have knowledge of where I may be able to obtain these sensor''s, or what IC may have been used in the sensor's construction, or information how to modify the  circuit to work with current Temperature sensor IC's

Many thanks, in advance

David  VK4WDH

hiska at powerup.com.au

Sponsored by the City of Tempe 

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