Automated Guarded Bridge for Calibration of Multimegohm Standard Resistors - Electronic Circuits Projects Diagrams Free

tswan · 7th November 2009, 03:19 AM

I've trying to understand this paper:

http://ts.nist.gov/MeasurementServic...ded-bridge.pdf

The Wheatstone bridge is no problem, but I just don't understand how the author's bridge using 2 supplies works. In the paper he says that the detector measures the difference of the the currents flowing through Rx and Rs, but it sure looks like the detector would measure the sum of these two currents.

I know I'm not understanding something fundamental and I'm hoping someone here might be able to explain to me why adjusting the voltages will null out the current.

Thanks.

JimB · 7th November 2009, 04:55 AM

I agree with you, as fig 2 in the paper is drawn, the current through the detector will be the sum of the currents in the two resistors.
If the polarity of one of the voltage souces is reversed then the current through the detector will be the difference of the two resistor currents.

JimB

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar
Title	Starter	Forum	Replies	Latest
Automated battery charger	Valentine	General Electronics Chat	5	31st July 2009 06:12 PM
Automated christmas lights	pdelass	Electronic Projects Design/Ideas/Reviews	4	26th December 2008 12:36 PM
Automated text pls help	shino9875369	Electronic Projects Design/Ideas/Reviews	0	14th October 2008 02:11 AM
Automated location finder.	Misc	Robotics Chat	8	14th November 2006 12:43 PM
Automated Altimeter?	tipc	Robotics Chat	1	6th May 2004 11:11 PM

7th November 2009, 03:19 AM	#1
tswan	Automated Guarded Bridge for Calibration of Multimegohm Standard Resistors I've trying to understand this paper: http://ts.nist.gov/MeasurementServic...ded-bridge.pdf The Wheatstone bridge is no problem, but I just don't understand how the author's bridge using 2 supplies works. In the paper he says that the detector measures the difference of the the currents flowing through Rx and Rs, but it sure looks like the detector would measure the sum of these two currents. I know I'm not understanding something fundamental and I'm hoping someone here might be able to explain to me why adjusting the voltages will null out the current. Thanks.

7th November 2009, 04:55 AM	#2
JimB	I agree with you, as fig 2 in the paper is drawn, the current through the detector will be the sum of the currents in the two resistors. If the polarity of one of the voltage souces is reversed then the current through the detector will be the difference of the two resistor currents. JimB __________________ Experience is directly proportional to the value of the equipment ruined.