Exhaust Temperature Scanner Caterpillar

System Response

Conditions for Setpoints

If an alarm condition is detected, the scanner displays the output for the applicable channel. The top line displays the channel and the temperature of the cylinder or turbocharger. The second line displays "ALARM" and the description of the alarm. The display flashes. The state of the configured output switch changes.

Channels without alarm conditions will continue to display normally.

Illustration 1	g00765047
Typical displays for alarms (1) Exhaust port temperature deviation (2) High turbocharger inlet temperature (3) High turbocharger outlet temperature

Table 1 lists the alarms that can be displayed and a description of the alarm.

"ENTER/ACK" key

If an alarm is activated, the display will continue to flash until the alarm is acknowledged with the "ENTER/ACK" key. When the "ENTER/ACK" key is pressed during an alarm condition, flashing of the display ceases.

"RESET" key

If another alarm exists, the output switch is cleared for five seconds. After the five seconds have elapsed, the state of the output switch changes again. Any alarm that has not been acknowledged will flash when that setpoint is viewed on the display. The display will continue to flash for each alarm until one of the following conditions occurs:

• The alarm is no longer active.

• The alarm is acknowledged.

• The "RESET" key is pressed.

The "ENTER/ACK" key acknowledges each individual alarm. The "ALARM" indication will continue to display for all active alarms that are acknowledged but not reset.

The "RESET" key acknowledges all of the alarms. The key also resets the alarms.

Both latching output and nonlatching output are cleared when an alarm is acknowledged.

For an alarm that ceases without being acknowledged, the two types of outputs react differently:

• The output of a nonlatching switch is automatically cleared when the alarm ceases.

• Latching output must be cleared by the operator.

The default configuration of the output switches is nonlatching.

Use any of the following methods to acknowledge alarms for latching output:

• Acknowledge each individual alarm until all of the alarms have been acknowledged.

• Press on the "RESET" key for three seconds.

• Cycle the power.

Pressing on the "RESET" key for three seconds or cycling the power performs the following functions:

• The system is reset for all alarms that have occurred.

• Output is cleared for all alarms that have not been acknowledged.

• The start-up timer is reset.

Conditions for System Diagnostics

The scanner responds to two conditions that are not programmable as setpoints for alarms:

• Temperatures that are out of range

• Open circuits for thermocouples

The range of temperatures for the scanner is 0 to 850 °C (32 to 1562 °F). If a monitored temperature falls below the minimum, "X LO OOR" is displayed in order to indicate that the channel is out of the low end of the range. "X" represents the number of the channel.

If a monitored temperature rises above the maximum, "X HI OOR" is displayed in order to indicate that the channel has exceeded the high end of the range. In either case, the minimum value or the maximum value is calculated in the average temperature for cylinder exhaust.

If a circuit for a thermocouple becomes open or if the wiring for the circuit is disconnected from the scanner, "X TCOPEN" is displayed in order to indicate the open circuit. For this condition, no value for the channel is calculated in the average temperature of cylinder exhaust. If the setpoint for a parameter of the channel is configured, the output switch will activate. All unused inputs for thermocouples must be shorted in order to prevent this condition.

Priority of Alarm Conditions

If more than one alarm occurs, the alarm that occurs first is displayed first. However, one channel could have more than one alarm occurring simultaneously.

There are three levels for two sets of priority for alarm conditions. One set is for the cylinders and the other set is for the turbochargers.

The setpoints have a priority because there is more than one setpoint associated with each channel. If more than one alarm occurs simultaneously for one channel, the alarm with the highest priority is displayed first.

Table 2 lists the priority of the alarm conditions.

Note: No priority is listed for high turbocharger inlet temperature ("TI HI"). Unless the setpoint is programmed for a lower temperature than the setpoint for turbocharger outlet temperature ("TO HI"), "TI HI" will be detected first.