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Tester or
Instrumentation Circuits, Page 13 Testers:
#'sA-BCDEF-GH-KLM-OPQ-RSTUV-Z Last Updated on:
Monday, October 03, 2011 06:08 PM
Circuits
Designed by Dave Johnson, P.E. :
TEMPERATURE
SENSOR WITH 4 TO 20mA CURRENT LOOP
I designed a circuit similar to this one years ago to accurately measure the air
temperature inside a building 1000s of feet from a control room. The circuit
uses the very robust current loop method. It uses a highly accurate
semiconductor temperature sensor and an equally accurate voltage reference. The
circuit includes a diode bridge, so it is polarity independent. By using the
component values indicated, the circuit should not require calibration. It has
a range from –40F to +120F and an accuracy of plus or minus one degree F.
Links to electronic circuits,
electronic schematics, designs for engineers, hobbyists, students & inventors:
Talking Voltmeter - Ever needed to measure a voltage without
taking your eye off something? If so, then this is the project for you! The
Orton Talking Voltmeter takes a voltage measurement in the range 0-5 Volts
and then reads it out to you to two decimal places (i.e. to 10mV
resolution). The design illustrates the use of the 10 bit ADC in the PIC,....(added
04/04/04)
TC64X/TC64XB Evaluation Kit for Fan Speed Controllers - This is a
complete evaluation board for evaluation and prototyping brushless DC fan
control circuits using the TC642, TC646, TC647, TC648, and TC649 BDC fan
controllers. (app note added 3/05)
Technique Measures Small Capacitance - 09/01/97 EDN-Design Ideas.... EDN is
migrating links. This link is not verified. Search the "title" + "EDN" for new
link.
Temperature controller has "take-back-half"
convergence algorithm - 15-Sep-05 Issue of EDN Enhanced closed-loop
control balances stability, responsiveness.... [Design Idea by W Stephen Woodward,
University of North Carolina, Chapel Hill, NC; Edited by Brad Thompson and Fran
Granville]
Temperature Monitor - Using a thermistor in the position shown makes a heat
activated sensor. A change in temperature will alter the output of the opamp and
energize the relay and light the LED. Swapping the position of the thermistor and 47k
resistor makes a cold or frost alarm.... [Andy Collison]
Temperature monitor measures three thermal zones - 11-Dec-03 Issue of EDN
You can use an ADT7461 single-channel temperature monitor; an ADG708 low-voltage,
low-leakage CMOS 8-to-1 multiplexer; and three standard 2N3906 pnp transistors to
measure the temperature of three separate remote thermal zones (Figure 1).
Multiplexers have resistance, RON, associated with them; the channel matching and
flatness of this resistance normally result in a varying temperature offset....
[Design Idea by Susan Pratt, Analog Devices, Limerick, Ireland]
Temperature Sensor with 4 to 20ma Current Loop - I designed a circuit
similar to this one years ago to accurately measure the air temperature inside a
building 1000s of feet from a control room. The circuit uses the very robust
current loop method. It uses a highly accurate semiconductor temperature sensor
and an equally accurate voltage reference. The circuit includes a diode bridge, so it
is polarity independent. By using the component values indicated, the circuit
should not require calibration. It has a range from –40F to +120F and an
accuracy of plus or minus one degree F. …. [Designed by David A. Johnson]
Temperature/ Light Brightness Meter with LCD - Circuit measures the
temperature and ambient brightness of the surrounding environment at the location it
is placed. The data from the ADC is the calculated and displayed on the LCD. The main
CPU unit on board the device is the PIC16F873. ….(electronic schematic added 11/08)
