YSI ProDSS - Manual (Page 41)

39
Calibration
pH/ORP
Figure 50 Calibrate pH 1-point
pH calibration 1-point
NOTE: If performing a 1-point calibration, use buffer 7 (6.86) as
your calibration point for highest accuracy.
NOTE: Observe the pH mV readings during calibration to
understand the condition and response of the pH sensor.
In buffer 7, pH mVs should be between -50 and +50. In
buffer 4, the mVs should be a +165 to 185 away from the
pH 7 mV value or a 59 mV per decade slope. In buffer 10,
the mVs should be a -165 to -185 away from the pH 7 mV
value or a -59 mV per decade slope.
1. Perform the Calibration setup (pH, ORP, ISE, conductivity, turbidity)
on page 33 .
2. Fill the calibration cup to the appropriate level (170 mL) with pH 7
buffer solution (or 6.86 if using NIST buffers).
3. Carefully immerse the probe end of the sensors into the buffer
solution.
4. Push the Cal key, then select pH or pH/ORP.
NOTE: If using a pH/ORP sensor, select pH/ORP, then pH.
5. Allow at least one minute for temperature stabilization, then
select Calibration value.
6. Enter the pH buffer value that corresponds to the measured
temperature reading (example: the value of pH 7 buffer solution @
20 °C (68 °F) is 7.02 - this value can be found on the bottle of most
pH buffers).
7. Observe the actual measurement readings for stability (white line
on graph shows no significant change for 40 seconds), then select
Accept Calibration ( Figure 50 ). “Ready for cal point 2” will be
displayed in the message area.
8. Select Finish Calibration for a 1-point calibration or continue on
to the 2-3 point calibration procedure ( Calibration cup installation
on page 34 ).