Sentry SP400 Instruction Manual download pdf (Page 53)

SMC sierra monitor corporation Sentry Instruction Manual - Version 6

CALIBRATION

Page: 47

5. CALIBRATION

5.1 SENTRY CALIBRATION - AN OVERVIEW

Calibration is a simple three step process:

1. Initiate calibration via the controller keyboard.

2. Apply zero gas (if required) and then span gas to the

sensors.

3. Close the calibration via the controller keyboard.

Calibration parameters are configured via the CHANGE

CALIB activity and are saved by Sentry for future calibrations.

During calibration Sentry "peak holds" the sensor signal output

for zero and span gas and then uses those values to construct a

curve for continuous reference during normal gas monitoring.

There are two alternative calibration methods, Global

Calibration and Local Calibration.

5.1.1 GLOBAL CALIBRATION

When Global Calibration is selected, the Sentry controller

collects zero and span value data from all sensor modules

eligible for calibration based on a global keyboard command. It

is not necessary to calibrate all the sensors, those which do not

receive span gas will be rejected automatically.

The operator presses the ENTER key to initiate, and complete,

collection of the zero value and then the span value. Calibration

gas may be delivered to the sensor module in a variety of

methods dependent upon the accessibility of the sensor.

The benefits of Global Calibration are:

• Magnetic calibration head not required.

• All "zero's" can be set at one time.

Global Calibration is particularly useful when:

• The sensor is in a position which is difficult to

access, because a calibration gas delivery tube can be

installed to a more accessible location.

• The magnetic head is not available or the magnetic

switch in one of the sensors is not functioning.

5.1.2 LOCAL CALIBRATION

When Global Calibration is turned off, the Sentry controller

collects zero and span value data from each sensor module

eligible for calibration based on a local command at the module.

Calibration gas is delivered through a magnetic fitting which

causes a switch in the sensor to command the controller to

remember the module output. The procedure calls for the

magnetic cap to be applied twice (zero first, span second)

except that the magnet is applied only once for oxygen modules.

The benefits of Local Calibration are:

• Individual modules can be calibrated while others

remain on line.

• Time savings when sensors must be exposed to zero

air due to the environment.

Local Calibration is particularly useful when:

• Plant operating procedures demand that some

modules remain on line while others are being

calibrated.

5.2 CALIBRATION INITIALIZATION

5.2.1 MODULES

Before any module can be calibrated it must be initialized via

the CHANGE MODULE activity. Initialization includes

turning the module on, setting the alarm levels and setting the

factor(s). This activity is described in step by step form in

Section 4.3 steps 6 through 18. If a module is not initialized, an

error prompt INITIALIZE MODULES FIRST will display

when calibration is attempted.

NOTE

The following calibration instructions are applicable to

controllers with version 6.xx firmware. For earlier

version firmware (example 4.2) refer to the Instruction

Manual furnished with that controller. To determine the

firmware version installed in any Sentry controller, press

TEST, ENTER and observe the firmware version number

on the lower LCD screen.

NOTE

If any sensors are not previously calibrated use

Diagnostic Code 0020 or 0021 to force calibration prior

to performing the normal calibration procedure. See

Section 8.3.5.

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