MODEL | SECTION 10.0 |
| CALIBRATION – PH |
10.3 PROCEDURE — MANUAL TWO-POINT BUFFER CALIBRATION
1.Obtain two buffer solutions. Ideally, the buffer values should bracket the range of pH values to be measured.
2.Remove the pH sensor from the process liquid. If the process and buffer temperatures are appreciably different, place the sensor in a container of tap water at the buffer temperature. Do not start the calibration until the sensor has reached the buffer temperature. Thirty minutes is usually adequate. Make a note of the temperature.
3.Press MENU. The main menu appears. Choose Calibrate.
4.Choose pH.
5.Choose BufferCal.
6.Choose Manual.
7.Choose Buffer1.
8.Rinse the sensor with water and place it in buffer 1. Be sure the glass bulb and reference junction are com- pletely submerged. Swirl the sensor.
9.The reading in the top line is the live pH reading. Wait until the live reading is stable. Then, use the arrow keys to change the reading in the second line to the match the pH value of the buffer. The pH of buffer solutions is a function of temperature. Be sure to enter the pH of the buffer at the actual temperature of the buffer.
10.Remove the sensor from buffer 1 and rinse it with water. Place it in buffer 2. Be sure the glass bulb and the reference junction are completely submerged. Swirl the sensor. Choose Buffer2.
11.The reading in the top line is the live pH reading. Wait until the live reading is stable. Then, use the arrow keys to change the reading in the second line to the match the pH value of the buffer. The pH of buffer solutions is a function of temperature. Be sure to enter the pH of the buffer at the actual temperature of the buffer.
12.The screen at left appears momentarily.
13.If the calibration was successful, the transmitter will display the offset and slope (at 25°). The display will return to the screen in step 5.
14.If the slope is out of range (less than 45 mV/pH or greater than 60 mV/pH) or if the offset exceeds the value pro- grammed in Section 8.4, an error screen appears. The display then returns to the screen in step 6.
15.To return to the main display, press MENU then EXIT.
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