RALPH G WASHBURN
Radio and Television Technicians in Marion, MA

4041382, Aug 9, 1977

Aug 16, 1976

5/714386

Ralph G. Washburn - Marion MA

The Sippican Corporation - Marian MA

G01R 2702

324 65R

A measurement system of the type having a sensor the electrical resistance of which varies as a function of a parameter being measured, and a bridge circuit connected to the sensor, wherein a source of a reference voltage is provided to excite the bridge to produce a bridge output indicative of the parameter being measured when the bridge is balanced, the bridge output being dependent upon the sensor resistance and the reference voltage except that the system includes circuitry for causing the output to be independent of the reference voltage at one end of a range of values of the parameter, and output circuitry is provided for converting the bridge output into a system output in accordance with an output function, featuring, in one aspect, first calibration circuitry connected to the output circuitry to provide a first calibration signal for calibrating the system at one end of the range by controlling the output function; second calibration circuitry connected to the bridge circuit to provide a second calibration signal for calibrating the system at the other end of the range by controlling the effective value of the reference voltage supplied to the bridge circuit; sequencing circuitry for automatically causing the first calibration circuitry to calibrate the system at one end of the range, and then automatically causing the second calibration circuitry to calibrate the system at the other end of the range; and a control for activating said sequencing circuitry.

4025847, May 24, 1977

Aug 27, 1975

5/608030

Ralph G. Washburn - Marion MA

The Sippican Corporation - Marion MA

G01R 2702

324 65R

In a measurement system having a sensor the electrical resistance R. sub. s of which varies as a function of a parameter being measured, and a bridge circuit having the sensor and a long transmission wire in a first arm connected to a first control node, a second long transmission wire in a second arm connected to a second control node, and third and fourth arms respectively connected to the first and second nodes, the wires having equal resistances R. sub. c, the wires being connected to the sensor and being arranged so that any resistance-changing conditions affect both wires equally during operation of the system, that improvement wherein the third bridge arm is connected between the first control node and a first current injection node, the fourth bridge arm is connected between the second control node and a second current injection node, a reference voltage source is provided, first active control circuitry is connected to receive inputs from the first and second control nodes and from the voltage source, and to provide to the first injection node a current controlled so as to maintain the control nodes at a predetermined voltage difference related to the voltage at the source, second active control circuitry is connected to the bridge to provide to the second injection node a current controlled so as to maintain the injection nodes at a voltage difference related to the predetermined difference, and output circuitry is connected to the bridge to provide an output related to one of the controlled currents.

4359285, Nov 16, 1982

Apr 16, 1980

6/140800

Ralph G. Washburn - Marion MA

The Sippican Corporation - Marion MA

G01D 304, G01K 120

374172

In a temperature probe having a thermistor controlling the output frequency of an oscillator to effect a temperature-frequency conversion, and a remote measuring station having a frequency detection means, the invention features, generally, a switch in the probe connected to a detection circuit, the oscillator being connected to the switch so as to open and close the circuit in response to the oscillator output frequency.