Measurements Group Strain Gauge Instrumentation

Model 1550A Strain Indicator Calibrator 

However, the 'star network' cannot simulate quarter-bridge strain gauge behavior, and cannot simulate positive strain. Another serious problem with this circuit is that the bridge input and output resistances change in an abnormal manner, leading to inaccuracies in calibration under some conditions.

A calibrator based on the Wheatstone bridge principle requires stable components. A total of 66 ultra-stable Vishay precision resistors are used in the Model 1550A calibrator to provide the stability, repeatability, accuracy and incremental steps required in a laboratory standards instrument.

A Certificate of Calibration is provided with each Model 1550A Calibrator. 

Features

• True Wheatstone Bridge Circuitry

• Simulates Quarter, Half & Full Bridge - both 120 ohm/350 ohm

• 3 Decades of Push Buttons

• Strain Range Direct Reading: +99 900 microstrain... Increments of 100 microstrain 

• Transducer Range: +49.95 mV/V... Increments of 0.05 mV/V 

• Reversing Switch for Plus and Minus Calibration

• High Precision Vishay Resistors used throughout to ensure Excellent Stability

• Accuracy 0.025 Percent - Traceable to the U.S. National Institute of Standards and Technology 

Specifications
All specifications nominal or typical at +23 deg C unless noted.

Accuracy:
0.025% of setting +1 microstrain (0.0005 mV/V), max. Traceable to United States National Institute of Standards and Technology.

Repeatability:
+1 microstrain (0.0005 mV/V), max.

Stability:
(0.001% of setting +1 microstrain/deg C), max.

Thermal EMF:
0.5 microvolt/volt of excitation, max.

Bridge Resistances:
120 ohm and 350ohm.
Input resistance: +0.05%, max., from nominal at all output settings.
Output resistance: +0.05%, max., from nominal at "000" microstrain, -0.25% at +99 900 microstrain.

Circuit:
True +in two adjacent arms (opposite signs), plus two fixed arms for bridge completion.

Simulation:
Quarter bridge, one active arm. Half bridge, one or two active arms. Full bridge, two active arms.

Range:
Two active arms: 0 to +99 900 microstrain in steps of 100 microstrain at GF=2.00. 0 to +49.95 mV/V in steps of 0.05 mV/V.
One active arm: 0 to +49 950 microstrain in steps of 50 microstrain at GF=2.00.

Excitation:
To meet accuracy and repeatability specifications:
120 ohm: Up to 10Vdc.
350 ohm: Up to 15Vdc.
Maximum permissible:
120 ohm: 25V ac or dc. 350 ohm: 30V ac or dc.

Output at 000:
50 microstrain (0.025 mV/V), max. in full-bridge mode.

Environment:
Temperature: +50 deg to +100 deg F (+10 deg to +38 deg C).
Humidity: Up to 70% RH, non-condensing.

Size: Aluminum case (separable lid). 5-3/4 H x 8-1/4 W x 7-3/4 D in (145 x 210 x 195 mm).

Weight: 4.8 lbs (2.2 kg).