Honeywell UDA2182 Running a Probe Bias Scan Introduction, Test initiation, Pressure Sensor Cal

Input Calibration

Step	Action	Screen
4	Press Enter	“Pressure Sensor Cal”
		Display shows the barometric
	Follow the prompts at the top	pressure value in mm Hg.
	and bottom of the screen.	“Press Enter when stable”
5	Once the reading is stable,	Change to sample value”
	press Enter	Use the arrow keys to change
		the displayed value until the
		displayed pressure in mmHg
		agrees with the known pressure.
		“Enter to save, Exit to cancel”
6		“ Cal Complete”
		This screen gives you an option
		to exit or recalibrate.
		Press ENTER to recalibrate.
		Press EXIT to return to Input Cal
		Screen.
7	If the calibration fails, an error	Error Messages:
	message will be displayed	See Table 12-2.
	across the bottom stripe of the
	screen.
	Make necessary adjustments
	and re-calibrate.

Running a Probe Bias Scan

Introduction

The dissolved oxygen probe is an electrochemical cell, which produces an electric current that is directly proportional to the concentration of oxygen dissolved in the sample in which the probe tip is immersed. (When the probe is in air, the current is identical to that produced when the probe is in air-saturated water.) This current is a direct measurement of oxygen level. Usually, the probe is operated at -0.55V with respect to a reference electrode within the probe. (The minus sign is omitted from the screen as well as from the following discussion.) However, in some applications, the performance of the DO probe can be enhanced by using other bias voltages. The purpose of this test is to evaluate whether the probe bias voltage should be adjusted. Possible interference with probe performance may also be inferred from the Probe Bias Test (PBT).

Test initiation

When the test is initiated, the bias voltage is adjusted down from its original value (usually 0.55V) at 25mV/sec until 0V is reached. Then the bias voltage is driven up to 1.0 V at 25mV/sec and finally, it is driven down again until it has returned to the value it had just

172 UDA2182 Universal Dual Analyzer Product Manual January 2009