Eureka Manta Manual
Page 27 of 67
4
Rinse the sensors twice with a small quantity of your calibration standard. Discard the used calibration
standard.
5
Immerse the sensor in the calibration standard. This is usually accomplished by pouring the standard
into the Manta’s calibration cup once it has been screwed onto the Manta housing. Secure your
Manta with the sensors pointing up and fill the calibration cup with your calibration standard. Make
sure the standard covers the sensor entirely, and that it also covers the thermistor for those
parameters that are temperature-compensated. For turbidity sensors and other fluorometers fill the
cup to at least 1 ½ inches above the sensor’s lens surface.
6
Select the parameter to be calibrated by clicking on the Manta pull-down menu in the Home Page,
then clicking on Calibrate, and then clicking on the parameter you wish to calibrate. First, enter the
calibration value and press enter; when the reading has stabilized, press enter to calibrate. The Manta
will report the resulting Sensor Response Factor (SRF); then press Y to accept the calibration, N to
back up one step, or Exit to leave the sensor uncalibrated. (C.5.e)
D.3 Choosing Calibration Standards
For best results, choose a calibration standard whose value is close to what you expect to see in the field.
For example, calibrate with a 1413 μS
/cm Specific Conductance standard if you expect to see Specific
Conductance reading
s between 500 and 1000 μS
/cm in the field. Calibrating with a sea water standard
or a very low standard would not be appropriate in that case. Similarly, if your waters tend toward the
acidic, calibrate with a 4-buffer instead of a 10-buffer.
If you are moving your multiprobe across wide ranges of water conditions, you may wish to recalibrate to
match the new situations. For instance, if you are measuring a clear lake during the morning and a high-
sediment stream in the afternoon, you might consider recalibrating at noon with a high-range turbidity
standard.
The table below shows common calibration practices.
Sensor
Standard Method of Calibration Available Calibration Solutions
Comments
Temperature
never requires calibrating
N/A
pH / pH reference
2 or 3 points
pH 4, pH 7, pH 10
pH7, pH 10 most common
ORP
1 point
ORP Standard 200 mV
Conductivity
1 point
CD Standard, 0.5 Molar, 58670 Micro S
CD Standard, 0.1 Molar, 12856 Micro S
CD Standard, 0.01 Molar, 1412 Micro S
CD Standard, 0.001 Molar,147 Micro S
brackish/saltwater
borderline brackish typical
freshwater very pure
fresh/glacial
