Measurement-computing StrainBook/616 Bedienungsanleitung PDF herunterladen (Seite 46)

4-16 Software 967594 StrainBook/616 User’s Manual

Shunt (Internal Shunt) Calibration

The Shunt calibration method pertains to an internal shunt. For this method two readings are acquired from a

bridge. The first reading is obtained with the bridge in its quiescent state; the second is taken with one leg of the

bridge shunted by one of three selectable resistors. The resistors are located on a plug-in header inside the

StrainBook or WBK16 module. Shunt calibration appears as "Shunt (RB)", "Shunt (RD)", and "Shunt (RF)" in the

list of calibration methods.

The Internal Shunt Calibration requires that the user enter the following 7 parameters:

Excitation - The val

ue of the constant voltage source used to excite the gage.

Gage Factor -

The Gage Factor value of the gage used in the bridge. A Gage Factor of 2 is typical.

Shunt Ohms - The value in Ohms of the shunt resistor mounted on the header inside the StrainBook or

BK16 module.

Bridge Ohms -

The resistance value of the gage. Typically 120 or 350 Ohms.

Max Load - The m

aximum load value the gage is expected to measure. This value could be less than the

max rated load of the gage.

Quiescent Load - The at rest v

alue of the load applied to the gage. If no load will be applied to the gage in

its quiescent state, enter “0” zero.

Point 1 Units - The m

inimum load value the gage is expected to measure. This value could be greater than

the minimum rated load of the gage.

Example

: Excitation voltage is set to 2 volts. A Quarter Bridge circuit employing a 350 Ohm strain gage with a

Gage Factor of 2 and a full load rating of +/- 1500 µe is connected to a StrainBook [or WBK16 channel]. The gage

will be used in an environment were the expected range of measurement is limited to -200 to +1000 µe. This gage

[in its quiescent state] has a 500 µe load. A 349,650 Ohm precision resistor is available that will be mounted on the

plug-in header in Shunt location R(B). Instructions for installing shunt resistors are provided elsewhere in the

document. In this example the user would enter the following values in the Calibration Parameters spreadsheet:

Cal Method Shunt R(B)

Excitation = 2V.

Gage Factor = 2

Shunt Ohms = 349,650

Bridge Ohms = 350

Max Load = 1000

Quiescent Load = 500

Point 1 Units = -200

The accuracy of Shunt Calibration is directly related to the tolerances of the Shunt resistor, Gage(s), and Bridge

ompletion resistors used in the circuit. In the event that a precision shunt resistor is unavailable, WaveView

provides an alternate way of calculating Shunt calibration constants. This method is as follows:

(a) Inst

all an appropriate non-precision shunt resistor of a value that creates the degree of bridge

imbalance desired.

(b) Press and hol

d the <Alt> key on the computer’s keyboard; then start the calibration process.

ted you release the <Alt> key.

This al

ternate Shunt Calibration method calculates the shunted load value from shunted and un-shunted bridge

voltage measurements; and then performs the equivalent of a 2 Point Manual calibration.

1 2 ... 41 42 43 44 45 46 47 48 49 50 51 ... 145 146

Kommentare zu diesen Handbüchern

Keine Kommentare

Measurement-computing StrainBook/616 Bedienungsanleitung Seite 46

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Hardware Measurement-computing StrainBook/616