installation steps
1. In any panel 1/16" (1.5mm) to 3/8" (9.5mm) thick, make a rectangular cut as shown in Figure 1.
Figure 1 Panel opening
2. Remove the mounting screws and mounting bracket from the panel of the meter and insert the panel meter into the opening
(See Figure 2).
Figure 2 Panel Meter with Mounting Brackets and Screws
3. Slide the mounting bracket and tighten the mounting screws to secure the panel meter to the mounting panel (see Figure 3).
Figure 3 Installation method
wiring diagram
1. Connect the AC power input and 4~20mA output (see Figure 4).
2. Connect a pH combination electrode with BNC connector to the BNC input (see Figure 4).
Figure 4 Rear panel wiring diagram
Measuring pH
1. pH calibration
1.1 Immerse the electrode in buffer solution 7.
1.2 Set the temperature control on the front panel to the temperature of buffer solution 7 (see Figure 5).
1.3 Set the calibration control of the meter to read the value corresponding to the buffer solution at the temperature set in 1.2 (see Table 1).
Figure 5 Front panel wiring diagram
1.4 Immerse the electrode in buffer solution 4 or buffer solution 10.
1.5 Set the temperature control to the temperature of buffer solution 4 or buffer solution 10 .
1.6 Set the slope control of the meter to display the value of the buffer solution at the temperature set in 1.5 (see Table 1).
1.7 The instrument has been calibrated and can be used for testing.
4~20mA output
1. Normal mode
Set the MODE switch on the rear panel to the NOR. (normal) position (see Figure 4). The 4~20mA output is preset to: 4mA at pH 0 and 20Ma at pH14.
2. Extended mode
Set the MODE switch on the rear panel to the EXP. (extended) position (see Figure 4). 4~20mA output is extended to cover any 2pH unit. Use a screwdriver to adjust the center of the 4~20mA output through the hole below the MODE switch.
2.1 Connect a mA meter to the 4~20mA output.
2.2 Set the meter to the center of the required 4~20mA range, and adjust the 4~20mA control until the mA meter reads 12mA. The output will be 4 mA 1 pH unit and 20 mA 1 pH unit above the center value.
2.3 Examples
The center value of the Model 691 is set at pH 7.31. Its output will be 4mA at pH 6.31 and 20mA at pH 8.31.
output insulation
The transmitter output to ground is isolated from the pH test circuit. Since the input voltage from the pH electrode can be very different from the transmitter output load, isolation between the pH input and the transmitter output avoids introducing errors into the measurement system. For the Model 691N, this potential difference can be as high as 750VDC.
grounding
Preferably there is a third wire from the AC power cord to the metal meter case (see Figure 4).
