GF Signet 2850 Conductivity-Resistivity Sensor Electronics and Integral System - Manual (Page 6)

6 2850 Conductivity/Resistivity Sensor Electronics
10. Calibration
• All 2850 Conductivity/Resistivity Sensor Electronics are factory calibrated for maximum out-of-the-box accuracy.
• The EasyCal feature allows calibration to be performed at the sensor.
10.1 EasyCal
EasyCal is a single-point calibration system. During this procedure, if the measured value is within ±10% of any of the test values listed
below, the 2850 will automatically recognize the test value and calibrate the output to that value.
Note:
The fi rst step (Reset) is recommended each time an electrode is replaced, but is NOT necessary upon initial installation or periodic
calibration.
1. Reset the 2850 Sensor to factory calibration: Set all switches on SW3 (and SW4 for dual input) to OPEN. Apply power, wait at least
3 seconds, then press and hold SW1 until the LED (D3) comes on steady then goes off again (approx. 10 seconds). When the LED
goes off, release SW1; reset is complete. Reset SW3 and SW4 to the proper settings.
2. Place the electrode/sensor assembly into the conductivity test solution appropriate to your operating range. Shake the electrode to
dislodge any air bubbles visible on the surface of the electrode.
• 146.93 μS, 1408.8 μS, 12856 μS (per ASTM D1125-95)
• 10 μS, 100 μS, 200 μS, 500 μS, 1000 μS, 5000 μS, 10,000 μS, 50,000 μS, 100,000 μS.
• Allow at least 2 minutes for the electrode response to stabilize.
3. Press and hold SW1 for approximately 8 to 10 seconds. During this time, the LED will come on steady then go back off. (If the LED
blinks several times rapidly, the calibration was not successful. See the troubleshooting section).
Calibration is complete. Return the system to service.
Calibrating the Dual-Input model 3-2850-63
• The 2850-63 can only be calibrated if both inputs are used, or if input 2 is disabled.
• To disable input 2: Set SW4, #4 to OPEN.
• Place each sensor into a test solution that represents the operating range of that sensor. When SW1 is pressed, the 2850 will
calibrate both inputs simultaneously.
• Dual input applications usually include one sensor with a smaller cell constant and one sensor with a larger cell constant. Place the
larger cell constant on input 1. This allows periodic recalibration of the larger cell by simply turning input 2 OFF.
a. SW2: 4 to 20 mA output range selection switch bank
b. Power and 4 to 20 mA or Digital (S
3 L) output terminal block
c. SW3 and SW4: Electrode Cell Constant selection switch banks
d. D3: LED indicator
e. SW1: EasyCal Push-button
f.
Conductivity Electrode connections
SW1
D3
1
2
3 1
2
3
4
ON
CTS
1
2
3
4
ON
CTS
1
2
3
4
ON
CTS
CH 1
CH 2
b
c
d
e
a
f
The 2839-2842 Conductivity sensors come with a certifi cate of calibration. This certifi cate provides information regarding the actual cell
constant and temperature offset as tested and verifi ed according to NIST standards. This information has been programmed into the
2850 electronics as its default factory value. If required, the sensor can be recertifi ed by contacting the GF Signet repair department.