Electro-Chemical Devices (ECD) T80 - Manual (Page 44)

Press Yes/NO Remove the Sensor from Solution and dry the front end, Air = 0.00 µS
To perform zero CAL press CAL 1, to skip zero cal press CAL 2, only if a zero cal was previously done on the sensor
Press AUTO then CAL 1 STABILIZING, 0.00 µS, 1.17 V, 0.00 µS corrected, Accept Cal?
Press YES CAL 1 Value 0.00 µS, Continue to CAL2? Move sensor to 1.00 mS solution
Press YES STABILIZING, 1.00 mS, 98X.X mV, 1.000 µS corrected, Accept Cal?
Press YES OFFSET: 0.00 ppm, 174.4 mV, SLOPE: 984 (data written to Log)
Press OK Calibration complete
Press HOME Hold is ON
Press HOLD Turn off Hold
Press EXIT Main Display
4.7.2 S
TANDARDIZE
With the sensor in the process solution, take a grab sample from the process and determine the conductivity
using a qualified laboratory conductivity meter.
Action Prompt
Double Press any Button MENU HOME, Hold is OFF
Press HOLD Hold freezes 4-20 mA Output and locks Alarm Relays during Calibration
Press CAL Is this a new Sensor? (Yes, erases CAL Log in INFO, NO adds CAL to existing Log)
Press NO With the sensor in the process solution
Press STAND Enter the laboratory determined conductivity value
Press ▲ ▼ NEXT xxx.xx µS/mS (use arrows and NEXT to enter process value)
Press OK xxx.xx µS/mS, xxx.x mV, Accept Value?
Press YES OFFSET: 0.00 µS 1.0 mV, SLOPE: xx.xx mV/ppm (this data written to Log)
Press OK Back to Cal Menu
Press HOME Hold is ON (Press HOLD to turn off Hold)
Press HOLD Turn off Hold
Press EXIT Main Display
4.8 TDS C
ONDUCTIVITY
S
ENSORS
The Total Dissolved Solids measurement (TDS) on the Model T80 transmitter is made with an S80 conductivity
sensor and a correlation factor. (Conductivity in µS x correlation factor = ppm)
Conductivity is a measurement of a solution’s electrolytic conductivity, 1/ohms. The type of dissolved ions in the
solution is irrelevant to the measurement. TDS is a measurement of concentration, ppm (mg/L). Since different
salts contribute different amounts of conductivity to a solution, TDS measurements are only valid between
solutions of the same chemical makeup. As an example, 1000 ppm of TDS in natural waters has a conductivity
around 1400 µS (correlation factor 0.6712), 1000 ppm of KCl has a conductivity around 2000 µS (correlation
factor 0.5000) and 1000 ppm of NaOH has a conductivity around 6000 µS (correlation factor 0.1667). All three
solutions have a TDS of 1000 ppm but the conductivities are 1400 µS, 2000 µS and 6000 µS. A TDS measurement
is only valid for a solution with the same chemical make up as the solution used for calibration.
Calibration is accomplished in two steps; Step 1 Conductivity AUTO Calibration of the sensor (see section 4.7.1
above) and then Step 2 correlation of conductivity to the TDS. The second step can be done by entering the
correlation factor into the CONFIG →SENSOR→ TDS menu or by standardizing the sensor in a solution of known
TDS in the CAL→STAND menu by entering the TDS value. Since the correlation of conductivity to concentration is
not linear it is best to calibrate the sensor near the measured value.
Page 43 Model T80