Some of these are:
• Recall and easy adjustment of relay and output parameters
• Push button calibration
• A HOLD function for outputs
• Continuous sensor check during measurement
• Continuous self check and watch-dog timer to ensure correct operation
• Password protection of stored values
• Temperature Output
• Simulated input for testing
4.2.1 The DOCN600 is calibrated at the factory, with the sensor purchased with the
instrument. However, the system should be field calibrated when installed and from
time to time thereafter. The calibration procedure is given in Section 5.3.
4.3 Temperature Compensation
4.3.1 A temperature sensor in the DOE-601 sensor provides the means of continually
compensating the D.O. reading for variation in the temperature of the process.
4.4 Relay Outputs
4.4.1 Three SPDT relays are provided. The normally open contacts, NO, are open when
no alarm or control is active.
4.4.2 The two control relay can be programmed to close on either rising or falling D.O.
They can be set to close at any point on the scale. The deadband, sometimes
termed hysteresis, defines the point at which the relays open. See Sections 4.8,
5.8, and 5.9.
4.4.3 The third relay functions as a high-low alarm. It has two programmable setpoints
(high and low). The deadband is fixed at 2% of full span. This relay is also
activated in the event of a perforated membrane. (See Section 4.5) The alarm
contact can be programmed to also signal memory loss in the DOCN600 controller.
See Section 4.8, 5.12, and 5.13.
4.4.4 All relays can be programmed for "fail-safe" operation which reverses the normal
operation of the relay. In this mode the relays will fail-safe (transfer) in the event of
4.5 Membrane Alarm Relay
4.5.1 A single pole double throw relay is provided to give an output in the event of a
4.5.2 This relay can be programmed to also signal memory loss. See Section 4.8.
4.5.3 When this relay is activated the contacts will close and the FAIL LED will be
indicated on the panel.