LOADING AWESOME
WHEATSTONE BRIDGE
www.propofology.com
Dr. David Lyness
@Gas_Craic
R2 x R3
R1
Rx =
LOADING AWESOME
Is an electrical circuit with one unknown resistor.
Used to measure an unknown electrical resistance.
Resistance of the unknown resistor is determined by pressure.
Thus, the resistor becomes a pressure gauge.
Used to measure an unknown electrical resistance.
Resistance of the unknown resistor is determined by pressure.
Thus, the resistor becomes a pressure gauge.
VG = Galvanometer/Ammeter
The strain gauge transforms strain applied to it into a proportional change in resistance. Thus, changes in resistance and current are measured, then electronically converted and displayed as systolic, diastolic and mean arterial pressures.
The circuit behind arterial line blood pressure monitoring
This setup of four strain gauges has the advantage that it is four times more sensitive than a single gauge Wheatstone bridge. It also compensates for any temperature change as all of the strain gauges are affected equally (temperature will affect the resistance of a strain gauge so in the single gauge setup, a change in temperature will skew readings).
The diaphragm is attached in such a way that when pressure is applied to it, gauges on one side of the Wheatstone bridge become compressed, reducing their resistance, whilst the gauges on the other side are stretched, increasing their resistance. The bridge then becomes unbalanced and the potential difference generated is proportional to the pressure applied.
