Det-Tronics MOS H2S Gas Sensor User Manual

Page 16

95-8532

1.4

Description

The Reset mode is entered by holding the Cal magnet to the side of the transmitter enclosure next to CAL/

RESET on the display face of the unit.
• Standard – When the Cal magnet is held there for less than one second, the alarm indicators turn off and

all relay outputs return to their normal condition if no alarms or faults are occurring.

• Forced – When the Cal magnet is held there for 1 to 2 seconds, the alarm indicators turn off and the

relay outputs return to their normal condition even if an alarm or fault condition still exists.

• Remote – Activating the remote reset switch for less than 2 seconds initiates a forced reset. If

“EXT CAL YES” was selected during the setup procedure, the external reset input initiates the

setpoint display cycle when activated for over two seconds.

When the Cal magnet is held to the side of the transmitter enclosure next to CAL/RESET for more than two

seconds, the transmitter enters the Setpoint Display mode. Once in this mode, the Cal magnet can be

removed. The Setpoint Display sequence will complete automatically. (The external reset input terminal can

also be used to initiate the setpoint display and calibration mode if “EXT CAL YES” was selected during the

setup procedure.) In this mode:
• The display sequentially shows the alarm setpoints, calibration gas concentration, as well as sensor

sensitivity and other information. Refer to “Table 5-Setpoint Display Cycle” for additional information.

• Each value is displayed for approximately 1.5 seconds.

• After completing the sequence, the transmitter automatically returns to the Normal operating mode if the Cal

magnet is no longer being held to the unit (or the external reset input is not activated).

NOTE

If the CAL/RESET switch (or external reset input) is still activated at the end of this cycle,
the transmitter automatically enters the Calibrate mode. If a calibration is not performed,
a CAL ABORTED fault will occur. To exit the Calibrate mode without performing the
calibration, cycle power or wait for the calibration fault message, then reset the unit.

The Setpoint Display mode only displays the setpoints. Use the “Setup” mode for changing setpoints.

• Auto Cal is an automatic calibration procedure that requires no adjustments by the operator. The Calibrate

mode is entered by holding the Cal magnet to the CAL/RESET magnetic switch until completion of the

“Setpoint Display” sequence described above (approximately 7 seconds). (The external reset input terminal

can also be used to enter the calibrate mode if “EXT CAL YES” was selected during the Setup procedure.

Activate the input until completion of the “Setpoint Display” sequence.)

• The transmitter performs the Zero adjustments, then signals the operator when to apply and also when

to remove the calibration gas. Upon completion of a successful calibration, the transmitter automatically

returns to the Normal operating mode.

• If the operator fails to complete the calibration procedure, if an error in calibrating occurs, or if a successful

calibration cannot be completed, the transmitter will automatically return to the Normal mode and continue

to use the previous calibration data (after 10 minutes or when the gas level drops below the lowest alarm

setpoint). A fault indication will be displayed until a reset occurs.

• If the microprocessor determines that the sensor cell is approaching the end of its useful life, the message

“SENSOR” “AT E.O.L.” will be indicated on the display. A fault indication will be displayed until a reset

occurs.

• While in the Calibrate mode, all transmitter outputs are inhibited and the dc current output goes to a preset

level (adjustable from 0 to 20 ma, with a default value of 2.0 ma). See “Setup” section for complete calibration

procedure.

In the setup mode, the range (for some gases), alarm setpoints, calibration gas level, current loop levels,

relay operation (latching/non-latching, energized/de-energized), and calibration mode (auto/manual) are

programmed into the transmitter.

NOTE

When using MOS H

S sensors, only 40 ppm H

S in air may be used for span calibration.

The transmitter will not read accurately if other concentrations are used.

Operating Mode

Reset

Setpoint Display

Auto Calibration

Setup

Table 4—Infiniti Modes of Operation (Continued)