8850-1eng 电导率表说明书(7)

GF 8850电导率表说明书

Temperature Coefficient

Conductivity measurement is highly dependent on temperature. Temperature dependence is expressed as the relative change per °C,commonly known as percent/°C change from 25°C, or slope of the solution.

Slopes can vary significantly depending on process solution type. The factory default temperature compensation factor is 2.00%/°C.Process solutions may require adjustment for maximum accuracy. To determine the optimum temperature compensation factor for aprocess:

1.Disable the 8850 temperature compensation % factor by entering 0.00.

2.Heat the sample solution close to the maximum process temperature. Place sensor in the sample solution allowing several

minutes for stabilization. Access the VIEW menu and record the displayed temperature and conductivity values in the spacesprovided:

Displayed temperature:Displayed conductivity:

T1 = _______ °CC1 = _______ °C

(Do not use this procedure for solutions from 0.055 µS to 0.1 µS (10 M to 18 M ). An internal pure water curve is used for theseranges. The factory default setting of 2.00%/°C should be used.)

3.Cool the sample solution close to the minimum process temperature. Place sensor in the sample solution allowing several

minutes for stabilization. Record displayed temperature and conductivity values in the spaces provided:

Displayed temperature:Displayed conductivity:

T2 = _______ °CC2 = _______ °C

(A 10% change in conductivity between steps 2 and 3 is recommended.)4.Substitute recorded readings (steps 2 and 3) into the following formula: TC Slope = (C2 x (T1 - 25)) - (C1 x (T2 - 25))

Example: A sample solution has a conductivity of 205 µS @ 48°C. After cooling the solution, the conductivity was measured at150 µS @ 23 °C. (C1 = 205, T1 = 48, C2 = 150, T2 = 23)The TC is calculated as follows:

TC Slope = = = 1.42%/°C

(150 x (48 - 25)) - (205 x (23 - 25)) 3860

Parts Per Million (PPM) Factor

This feature is only applicable when PPM display units are selected. The programmable PPM Factor is adjustable from 0.01 to3.00 (factory default = 2.00).

Determine the best PPM Factor for a process solution by calculating the solution's conductivity (µS) and the percent of totaldissolved solids (PPM).

PPM Factor =

Total dissolved solids (PPM) PPM Factor

Solution conductivity = 400 µS/cm TDS = 200 PPM (mg/L)

TDS (PPM) =Example:

PPM Factor =

= 2.00 200 PPM

SIGNET 8850-1 Conductivity/Resistivity Transmitterpage 9 of 12