Hach 48685, Руководство пользователя

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2. Use the thermometer included with the Sample Heater to measure the temperature of the sample
in the analyzer sample cell. Put the thermometer in the cell and wait for the temperature to
stabilize. The difference between the temperature in the cell and the temperature shown on the
display is due to loss of heat between the cell and the heater. For operator convenience, enter a
calibration offset to adjust for the temperature loss (
Enter the calibration offset on page 14). If
necessary, insulate the sample lines to decrease the amount of heat loss.
3. The factory sets the PID parameters for the heater. The factory-set values are appropriate for
most applications. If it is necessary to change the PID parameters, refer to
Autotune
on page 14.
Enter the calibration offset
The calibration offset is the difference between the required analyzer set-point temperature and the
temperature in the sample cell. For example, if the required temperature is set to 50 ºC and the
measured temperature of the sample cell in the analyzer is 47 ºC, the calibration offset is -3 ºC.
Wide variations in the temperature of the incoming sample or sample flow rate may cause a
difference in the indicated process temperature. If temperature changes occur in the analyzer sample
cell, make sure that the temperature setting on the sample heater and the offset agree with the
required values.
If variations in the sample-intake temperature or flow cause temperature instability, change the offset
to adjust. Refer to
Sample Heater Specifications on page 3 to find the capability for the operating
conditions.
To enter a calibration offset:
1. Push the ADVANCE key until CAL shows in the lower display. Push the DOWN arrow to
decrease the value of the CAL offset by 3 ºC.
Note: If no CAL offset value is entered, the CAL offset value will be 0.
2. Push the ADVANCE key.
The sample heater returns to normal operation. The process temperature and the setpoint
indicator should read the same temperature value.
Autotune
The Watlow EZ-ZONE PM ExpressMicroprocessor-based Auto-tuning Control has PID (proportional
band, resent/integral and rate derivative) control capability. The factory sets the PID parameters for
the heater. These values suit most applications. If it is necessary to change these parameters, follow
the procedure below. This procedure allows the controller to automatically tune the parameters.
Note: For successful auto-tuning, the setpoint temperature should be set at least 10 ºC above the inlet temperature.
1. Push the UP and DOWN arrows and hold them for 3 seconds to access the Loc menu.
2. Push the UP arrow and change the upper display to 5.
3. Push the INFINITY key. The display returns to the Operation menu.
4. Push the ADVANCED key and scroll to the AUto menu.
5. Push the UP arrow and highlight YES .
The upper display flashes tune and then YES while the sample heater does the auto-tune
procedure. The temperature must cross the auto-tune setpoint five times to complete the
procedure. The controller installs the appropriate PID parameters and saves them in nonvolatile
memory. The sample heater will auto-tune itself around 90% of the set temperature value.
Controller setup menu
The operational setup of the PID controller depends on specifics of the use-case. The manufacturer
has set the controller to operate with the manufacturer's sample heater.
14 English