Thermo Fisher Scientific CyberScan PC 510 - Manual (Page 52)

Instruction Manual PC 510
48
15 ADDENDUM 2: CALCULATING TDS CONVERSION FACTORS
You can calibrate your meter using TDS calibration standard solutions. The calibration standard only
needs to give the TDS value at a standard temperature such as 25
°C. To determine the conductivity-
to-TDS conversion factor use the following formula:
Factor = Actual TDS
÷ Actual Conductivity @ 25 °C
Definitions:
• Actual TDS: Value from the solution bottle label or as a standard you make using high
purity water and precisely weighed salts.
• Actual Conductivity: Value measured using a properly calibrated
Conductivity/Temperature meter.
Both the Actual TDS and the Actual Conductivity values must be in the same magnitude of units. For
example, if the TDS value is in ppm the conductivity value must be in
µS; if the TDS value is in ppt the
conductivity value must me in mS.
Check your factor by multiplying the conductivity reading by the factor in the above formula. The result
should be in TDS value.
16 ADDENDUM 3: STANDARD pH BUFFERS
The following table shows the various pH values at different temperature of the solution during
calibration. The table also illustrates why a calibration value may be different from the buffer value at
25
°C.
Temperature USA Buffer NIST Buffer
( o C) pH 1.68 pH 4.01 pH 7.00 pH 10.01 pH 12.45 pH1.68 pH 4.01 pH 6.86 pH 9.18 pH 12.45
0 1.67 4.01 7.12 10.32 13.43 1.67 4.01 6.98 9.47 13.43
5 1.67 4.01 7.09 10.25 13.21 1.67 4.01 6.95 9.38 13.21
10 1.67 4.00 7.06 10.18 13.00 1.67 4.00 6.92 9.32 13.00
15 1.67 4.00 7.04 10.12 12.81 1.67 4.00 6.90 9.27 12.81
20 1.68 4.00 7.02 10.06 12.63 1.68 4.00 6.88 9.22 12.63
25 1.68 4.01 7.00 10.01 12.45 1.68 4.01 6.86 9.18 12.45
30 1.69 4.01 6.99 9.97 12.29 1.69 4.01 6.85 9.14 12.29
35 1.69 4.02 6.98 9.93 12.13 1.69 4.02 6.84 9.10 12.13
40 1.70 4.03 6.97 9.89 11.99 1.70 4.03 6.84 9.07 11.99
45 1.70 4.04 6.97 9.86 11.84 1.70 4.04 6.83 9.04 11.84
50 1.71 4.06 6.97 9.83 11.70 1.71 4.06 6.83 9.01 11.70
55 - 4.08 6.97 9.81 - - 4.08 6.83 8.99 -
60 - 4.10 6.98 9.79 - - 4.10 6.84 8.96 -
70 - 4.12 6.99 9.76 - - 4.12 6.85 8.92 -
80 - 4.16 7.00 9.74 - - 4.16 6.86 8.89 -
90 - 4.20 7.02 9.73 - - 4.20 6.88 8.85 -