Geokon 4580, Instruction Manual

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1. THEORY OF OPERATION
The Model 4580 Vibrating Wire Pressure Transducer is designed primarily for the measurement
of very small changes in pressure such as in weirs, streams, etc. A sealed version is also available
which can be used for accurate measurement of barometric pressure. However, the Model 4580-
1 Barometer as shown in Figure 2 is specially designed for this purpose.
The transducer consists of a double diaphragm capsule secured in a pressure chamber and
connected to a vibrating wire strain gauge. Vented capsules are used where barometric effects
need to be eliminated, such as in the weir and stream level measurements. In the case where the
sensor is used as a barometer, the capsule is evacuated. The vibrating wire is attached to the
capsule on one end and to the rigid housing on the other.
External pressure applied to the capsule causes it to compress and exert a force on the vibrating
wire gauge and this produces a change in wire tension and frequency of vibration. The change in
tension is proportional to the pressure and, through calibration, the pressure can be very
accurately determined.
Instrument Cable
Diaphragm Wire
Electromagnetic
Tripolar Surge Arrestor
Thermistor
Seal
Screw Coil
Figure 1 - Model 4580-2 Vibrating Wire Pressure Transducer
Figure 2 - Model 4850-1 Barometer