Siemens ET 77E Series Especificaciones descargar pdf (Pagina 30)

SD77

4.0 CALIBRATION

The E/P Transducer must be positioned so that it is upright and vertical. Tilting within 10 degrees of vertical will

not affect operation. If the transducer has been lying on its side, set the unit upright and allow approximately 15

minutes before performing calibration. This will allow the viscous damping fluid to collect at the bottom of the

transducer.

The restriction screw (stamped R) must be installed in its operating position. An instruction label on the transducer

explains what to do.

The transducer has two calibration adjustments: ZERO and RANGE. These are identified on the transducer and in

Figure 2-1.

The ZERO adjustment screw changes the operating level. Turning it clockwise raises the output pressure.

The RANGE adjustment screw is used to trim the span. Turning it clockwise narrows the output span. The RANGE

screw provides a limited amount of adjustment, approximate ±2% of span. Because of this limitation, it is important

to use an accurate multimeter.

4.1 TEST EQUIPMENT

The following equipment is required to calibrate the transducer. For any instrument, the test equipment used for

calibration should be at least twice as accurate as the instrument being calibrated.

1. 0-50 mAdc source

2. Digital Multimeter: Accuracy 0.1% of reading or better

3. Pneumatic Test Gauge: Range, 0-15 psig (0-30 psig for 3 to 27 psig output); 0.02 psi per division; accurate to

0.6% of full scale

4.2 PROCEDURE

Refer to Figures 2-1 and 2-6 for pneumatic and electrical connections.

1. Adjust the supply air source to the specified value and connect it to the transducer's IN port.

2. Connect the test equipment to the transducer.

3. Set the milliamp source to the starting point value for the input signal range (e.g. 4 mA for a 4 to 20 mA range).

Adjust the transducer's ZERO for a 3 psig output.

4. Set the milliamp source to the full-scale value for the input signal range (e.g. 20 mA for a 4 to 20 mA range).

Adjust the transducer's RANGE for a 15 psig output. Model 77-8 is adjusted for a 27 psig output.

5. The ZERO and RANGE adjustments interact. Repeat the above steps until the calibration is correct.

4.3 RANGE CHANGE

Change the transducer’s range by installing a different coil assembly. Refer to Parts List 12334PL, at the rear of this

Instruction, for coil assembly part numbers.

Refer to the procedures in Section 5 Maintenance to remove, install, and align the coil.

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Siemens ET 77E Series Especificaciones Pagina 30