Conrad Digital Thermometer Module With LED Display Kit 192147 Data Sheet
Product codes
192147
• If measurements are unavoidable with the casing open, then an isolating transformer
must be interposed, or, as already mentioned, the power must be supplied through a
suitable mains unit (that conforms to the safety regulations).
suitable mains unit (that conforms to the safety regulations).
• All wiring work must be done in dead state.
Product description
An electronic thermometer with 13 mm red LED-display. This thermometer can be used
at all places, where temperatures are to be measured from -50°C to +150°C with a high
degree of accuracy.
at all places, where temperatures are to be measured from -50°C to +150°C with a high
degree of accuracy.
The use of the thermometer ranges from measuring the room temperature, outside
temperature, flow and return of heating as well as in the car, caravan, boat, motor
caravan, weekend home, laboratory, air-conditioning, industry, handicraft, and much
more. With temperature sensor KTY 10.
temperature, flow and return of heating as well as in the car, caravan, boat, motor
caravan, weekend home, laboratory, air-conditioning, industry, handicraft, and much
more. With temperature sensor KTY 10.
This article was checked according to EMVG (EG-Guideline 89/336/EMC/
Electromagnetic Compatibility), and the corresponding CE-certification mark was
awarded.
Electromagnetic Compatibility), and the corresponding CE-certification mark was
awarded.
Any change in the circuit or use of components other than the specified ones will
make this certification null and void!
make this certification null and void!
Description of circuit
In principle, such an electronic thermometer is nothing else but a digital voltmeter
(DVM), which measures the changing voltage at a resistance divider. The circuit used for
this, ICL 7107, is a controller for automatic DVMs with automatic zero-offset adjustment
and display drivers.
(DVM), which measures the changing voltage at a resistance divider. The circuit used for
this, ICL 7107, is a controller for automatic DVMs with automatic zero-offset adjustment
and display drivers.
The circuit manages with a simple, un-stabilised supply voltage, which can come from a
wall power supply; the voltage regulator IC3 converts it into 5 V fixed voltage for IC1.
The negative auxiliary voltage, required in addition, is generated with the help of an
oscillator-cycle and CMOS-driver from IC2: These charge the electrolytic capacitor C1 to
approx. -4 V via C2 and D2; this voltage spreads internally through IC1 intern and
stabilises it.
wall power supply; the voltage regulator IC3 converts it into 5 V fixed voltage for IC1.
The negative auxiliary voltage, required in addition, is generated with the help of an
oscillator-cycle and CMOS-driver from IC2: These charge the electrolytic capacitor C1 to
approx. -4 V via C2 and D2; this voltage spreads internally through IC1 intern and
stabilises it.
IC1 has a separate driver with a steady-current output for each segment for controlling
the LED-displays. This obviates the need for segment pre-resistors for current limitation
and helps achieve a uniform brightness regardless of the voltage supplies from outside.
Even the most significant point on the left can be equipped with a normal seven-segment
display, even when at the most two segments are active here (either the ‘1’ [starting from
100°C] or the minus-sign [below 0°C]).
the LED-displays. This obviates the need for segment pre-resistors for current limitation
and helps achieve a uniform brightness regardless of the voltage supplies from outside.
Even the most significant point on the left can be equipped with a normal seven-segment
display, even when at the most two segments are active here (either the ‘1’ [starting from
100°C] or the minus-sign [below 0°C]).
The test signal is fed at the ICL 7107 via the connections 30 (earth side) and 31 (positive
pole); capacitor C7 serves for short-circuiting the possible alternating current parts (e.g.
spikes). The polarity of the voltage to be measured can be any, but must be done in the
way described here; because only in this way the minus-temperatures get a negative
sign that takes place through the following displacement:
pole); capacitor C7 serves for short-circuiting the possible alternating current parts (e.g.
spikes). The polarity of the voltage to be measured can be any, but must be done in the
way described here; because only in this way the minus-temperatures get a negative
sign that takes place through the following displacement:
In case of a normal digital voltmeter the reference point (common, pin 32), reference-
minus (-ref, pin 35) and earth-side of the incoming signal (in lo, pin 30) are connected
with one another. The polarity at the input 31 then decides the sign; it is positive if the
connection 31 has positive potential vis-à-vis 30, otherwise it is negative.
minus (-ref, pin 35) and earth-side of the incoming signal (in lo, pin 30) are connected
with one another. The polarity at the input 31 then decides the sign; it is positive if the
connection 31 has positive potential vis-à-vis 30, otherwise it is negative.