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Instruction Manual
LIQ_MAN_6081-P
Section 8: Programming the Transmitter
8.1
General
This section describes how to program the transmitter using the keypad.
1. Select the measurement to be made (pH, ORP, or Redox).
2. Choose temperature units and automatic or manual temperature mode.
3. Set a security code.
4. Make certain settings relating to HART communication.
5. Resetting factory default settings.
6. Selecting a default display screen and adjusting screen contrast.
8.2
Changing Start-up
When the 6081 is powered up for the first time, startup screens appear. The screens prompt the
user to enter the measurement being made, to identify the sensor being used, to select automatic
or manual pH correction and to select temperature units. If incorrect settings were entered at
startup, enter the correct settings now. To change the measurement, refer to Section 8.4.
8.3
Choosing and Configuring the Analytical
Measurement
8.3.1
Purpose
This section describes how to do the following:
1. Configure the transmitter to measure pH, ORP, or Redox.
2. Determine the location of the preamp.
3. If pH was selected, there are additional selections and settings to make:
a. choose a solution temperature correction curve or set a temperature coefficient constant
b. choose sensor isopotential
c. set reference impedance low or high
8.3.2
Definitions
1. MEASUREMENT. The transmitter can be configured to measure pH, ORP or Redox (opposite
sign of ORP).
2. pH SETTINGS. If pH is selected, there are additional settings to make.
a. PREAMPLIFIER. The raw pH signal is a high impedance voltage. A voltage follower or
preamplifier, located either in the sensor or transmitter, converts the high impedance signal
into a low impedance one. Normally, high impedance signals should be sent no further than
about 15 feet.
b. REFERENCE OFFSET. Ideally, a pH sensor in pH 7 buffer should have a voltage of 0 mV. The
difference between the measured voltage in pH 7 buffer and the ideal value is the reference
offset. Typically, the reference offset is less than 60 mV.
c. DIAGNOSTICS. The 6081 continuously monitors the pH sensor for faults. If it detects a fault,
the transmitter displays a fault message.
d. GLASS IMPEDANCE. The transmitter monitors the condition of the pH-sensitive glass
membrane in the sensor by continuously measuring the impedance across the membrane.
Typical impedance is between 100 and 500 MΩ. Low impedance (<10 MΩ) implies the glass
bulb has cracked and the sensor must be replaced. An extremely high impedance (>1000
MΩ) implirs the sensor is aging and may soon need replacement. High impedance might
also mean that the glass membrane is no longer immersed in the process liquid.
3. INPUT FILTER. The raw sensor current can be filtered to reduce noise. Filtering also increases
the response time. The filter is the time required for the input to reach 63% of its final reading
following a step change.
8.3.3
Procedure to configure: Measurement.
To choose a menu item, move the cursor to the item and press ENTER.
Programming the Transmitter
Programming the Transmitter
February 2014
23
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