Apparatus and method for calibrating span of pressure measuring instruments

Claim 2

In a pressure measuring instrument of the type including a sealed interior pressure chamber containing a fill-liquid and having diaphragm means to apply thereto an input pressure signal to be measured, said instrument further including sensing means responsive to the input pressure signal applied to said fill-liquid to produce a corresponding output signal; that improvement for calibrating the span of the instrument comprising: reference pressure means forming in integral part of said instrument and including means in communication with said fill-liquid to apply thereto a reference pressure of precisely-controlled predetermined magnitude; and said reference pressure means being activatable while said input pressure signal is stable to apply said reference pressure to said fill-liquid so as to produce from said sensing means an output signal corresponding to said reference pressure magnitude; whereby the span of the instrument can be monitored and adjusted as necessary to assure that the output signal will correspond exactly to said reference pressure magnitude.

Claim 3

Apparatus as in claim 1, wherein said reference pressure means comprises means defining a cavity containing fill-liquid in communication with said instrument fill-liquid; means operable with said cavity to develop said reference pressure; and means to activate said reference pressure means.

Claim 4

Apparatus as in claim 2, wherein said instrument comprises a pair of diaphragms to receive a differential input pressure to be applied to said instrument fill-liquid; the fill-liquid regions adjacent said diaphragms being connected by a passageway; said cavity forming part of said passageway.

Claim 5

Apparatus as in claim 2, wherein said reference pressure means further comprises an element in contact with said cavity fill-liquid; and means to effect movement of said element in said cavity to create said reference pressure in said cavity fill-liquid.

Claim 6

Apparatus as in claim 4, including electrically-operable means to effect said movement.

Claim 7

Apparatus as in claim 4, wherein said cavity is formed to provide an elongate dimension; said element comprising an object sized to move through said elongate dimension to produce said reference pressure.

Claim 8

Apparatus as in claim 6, wherein said means to effect movement comprises means to rail said object against the force of gravity and then to release said object to allow it to fall under the force of gravity to produce said reference pressure.

Claim 9

Apparatus as in claim 7, wherein said means to effect movement comprises magnetic means operable in response to a signal to raise said object.

Claim 10

Apparatus as in claim 8, wherein said magnetic means comprises a coil energizable by said signal.

Claim 11

Apparatus as in claim 7, wherein said object is a ball; said cavity comprising a cylindrical tube having a circular cross-section slightly larger than the diameter of said ball.

Claim 12

Apparatus as in claim 10, including a winding surrounding said tube for producing a magnetic field for raising said ball.

Claim 13

In a pressure measuring instrument of the type including means to receive an input pressure signal and sensing means responsive to said input pressure signal to produce a corresponding output signal; that improvement for calibrating the span of the instrument comprising: reference pressure means forming an integral part of said instrument and including a cavity containing fill-liquid in communication with said sensing means; and means to activate said reference pressure means while said input pressure signal is stable to develop in said fill-liquid a reference pressure of precisely-controlled predetermined magnitude so as to apply a corresponding force to said sensing means to develop therefrom an output signal corresponding to said reference pressure magnitude; whereby the span of the instrument can be monitored and adjusted as necessary to assure that the output signal will correspond exactly to said reference pressure magnitude.

Claim 14

In a pressure measuring instrument of the type including means to receive an input pressure signal and sensing means responsive to said input pressure signal to produce a corresponding output signal; that improvement for calibrating the span of the instrument comprising: reference pressure means forming an integral part of said instrument and including a cavity containing fill-liquid in communication with said sensing means; and means to activate said reference pressure means while said input pressure signal is stable to develop in said fill-liquid a reference pressure of precisely-controlled predetermined magnitude so as to apply a corresponding force to said sensing means to develop therefrom an output signal corresponding to said reference pressure magnitude; whereby the span of the instrument can be monitored and adjusted as necessary to assure that the output signal will correspond exactly to said reference pressure magnitude.

Claim 15

Apparatus as in claim 12, wherein said reference pressure means further comprises an element in contact with said cavity fill-liquid; and means to effect movement of said element in said cavity to create said reference pressure in said cavity fill-liquid.

Claim 16

Apparatus as in claim 13, including electrically-operable means to effect said movement.

Claim 17

Apparatus as in claim 13, wherein said cavity is formed to provide an elongate dimension; said element comprising an object sized to move through said elongate dimension to produce said reference pressure.

Claim 18

Apparatus as in claim 15, wherein said means to effect movement comprises means to raise said object against the force of gravity and then to release said object to allow it to fall under the force of gravity to produce said reference pressure.

Claim 19

Apparatus as in claim 16, wherein said means to effect movement comprises magnetic means operable in response to a signal to raise said object.

Claim 20

Apparatus as in claim 17, wherein said magnetic means comprises a coil energizable by said signal.

Claim 21

Apparatus as in claim 16, wherein said object is a ball; said cavity comprising a cylindrical tube having a circular cross-section slightly larger than the diameter of said ball.

Claim 22

Apparatus as in claim 19, including a winding surrounding said tube for producing a magnetic field for raising said ball.

Claim 23

In a pressure measuring instrument of the type including a sealed interior pressure chamber containing a fill-liquid and having a pair of diaphragms through which an input differential pressure may be applied to said fill-liquid, said instrument further including sensing means responsive to said differential pressure to produce a corresponding output signal; that improvement for calibrating the span of the instrument comprising: (1) reference pressure means forming an integral part of said instrument and including: (A) means forming a cavity having an elongate dimension; (B) a fill-liquid in said cavity in communication with said instrument fill-liquid; (C) an object in said cavity sized to provide a close fit with the cavity walls; (D) means to lift said object up in said cavity and to release the object for descent through said fill-liquid under the force of gravity to produce in said fill-liquid a highly-precise pressure pulse of substantially constant magnitude; and (2) means to activate said lifting means while said input differential pressure is zero to apply said reference pressure pulse to said fill-liquid so as to produce from said sensing means an output signal corresponding to said reference pressure magnitude; whereby the span of the instrument can be monitored and adjusted as necessary to assure that the output signal will correspond exactly to said reference pressure magnitude.

Claim 24

In a pressure measuring instrument of the type including a sealed interior pressure chamber containing a fill-liquid and having a pair of diaphragms through which an input differential pressure may be applied to said fill-liquid, said instrument further including sensing means responsive to said differential pressure to produce a corresponding output signal; that improvement for calibrating the span of the instrument comprising: (1) reference pressure means forming an integral part of said instrument and including: (A) means forming a cavity having an elongate dimension; (B) a fill-liquid in said cavity in communication with said instrument fill-liquid; (C) an object in said cavity sized to provide a close fit with the cavity walls; (D) means to lift said object up in said cavity and to release the object for descent through said fill-liquid under the force of gravity to produce in said fill-liquid a highly-precise pressure pulse of substantially constant magnitude; and (2) means to activate said lifting means while said input differential pressure is zero to apply said reference pressure pulse to said fill-liquid so as to produce from said sensing means an output signal corresponding to said reference pressure magnitude; whereby the span of the instrument can be monitored and adjusted as necessary to assure that the output signal will correspond exactly to said reference pressure magnitude.

Claim 25

Apparatus as in claim 21, wherein one of said diaphragms is a range diaphragm having a pre-set spring-rate and effective area; said reference pressure means being arranged to apply said reference pressure to said range diaphragm.

Claim 26

Apparatus as in claim 22, including a conduit leading from the lower end of said cavity to the region adjacent said range diaphragm.

Claim 27

Apparatus as in claim 21, wherein said output signal is electrical and said activating means comprises electrical-signal-responsive means; signal-monitoring means coupled to said instrument to receive the output signal thereof; and signal means adjacent said signal-monitoring means and coupled to said activating means to direct thereto an electrical signal for initiating an operation of said reference pressure means.

Claim 28

Apparatus as in claim 24, wherein said signalmonitoring means and said signal means are remote from said instrument.

Claim 29

Apparatus as in claim 25, including a valved manifold connecting the differential pressure to said diaphragms; and means for actuating the manifold valves to provide zero differential pressure to said instrument; said actuating means including means at said remote location for controlling the operation of said manifold.

Claim 30

Apparatus as in claim 24, wherein said cavity is formed by a cylindrical tube and said object comprises a ball in said tube.

Claim 33

The method of claim 28, wherein said reference pressure signal is developed by causing an object to move in a cavity containing said fill-liquid.

Claim 34

The method of claim 29, wherein said object is caused to move through at least a part of said cavity by the force of gravity.

Claim 35

The method of claim 30, wherein said object is first raised against the force of gravity by an externally-developed magnetic field, and then allowed to descend through the fill-liquid.

Claim 36

The method of claim 28, including the step of maintaining static pressure on said diaphragm means while operating said device.

Claim 39

The method of claim 33, wherein said object is caused to move through at least a part of said cavity by the force of gravity.