ParTech 7200, Инструкция по эксплуатации

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7200 Monitor Instruction Manual
8 Calibration
8.1 Calibration General
Calibration of the 7200 Monitor is very important, errors in the calibration process will affect the measurement
performance of the instrument. The following section describes the various aspects of calibrating the 7200 Monitor and
has been written with the understanding that the user has knowledge of the measurement being made.
When a new system is installed, a period of 4 hours should be allowed for the equipment to stabilise before calibration
commences. This is to enable the system to adjust to the “new” ambient conditions. This should not be considered as
a warm up time from power up, it allows the system to adjust from a warm store or office to a cold site.
Any containers used to store calibration samples should be cleaned prior to use. This is particularly important when
performing the zero point calibration on a low range sensor.
The most accurate method of calibration is using a primary standard, i.e. calibration in the actual solution against a lab
result. Where this is not possible or where the trend of the reading is necessary rather than an absolute value it is
acceptable to use a secondary standard.
Please read this section together with the section titled ‘Calibration – Equipment and Procedures’ found in the
instruction manual for the chosen sensor.
Note: Whenever the sensor type is changed, the factory default values for calibration are loaded for the new
sensor type.
8.2 Methods of Calibration
Primary Standard
This method of calibration will give the best results however it does require the use of a laboratory to carry out a
gravimetric analysis of the calibration solution. The result of the gravimetric analysis is used as the calibration value.
Secondary Standard
In cases where it is not possible to carry out calibration using a primary standard, secondary standards such as Fullers
Earth or Formazin can be used. It is important to remember however that instruments calibrated in this way will give
results based on the secondary standard used and this will differ from the results of a gravimetric analysis.
A guide to the preparation of Fullers Earth and Formazin solutions is located at the back of this manual.
Calibration Intervals
The 7200 Monitor and Sensor combination once calibrated will require calibration checking/re-calibration at 3-6
monthly intervals, however this does depend on the application. The calibration of the instrument can be effected by
seasonal variations in the measured effluent, however only knowledge of the application can determine the re-
calibration interval required.
8.3 Preparing for Calibration
To ensure that calibration will be as successful as possible the following should be observed:
•
Clean the whole sensor and at least 1 metre of cable.
•
The zero solution should be clean settled tap water for high range sensors and freshly distilled or de-
mineralised for low range sensors.
•
A calibration solution will be required; ideally this should be greater than 75% of the intended measurement
range.
167300IM-Issue 12 Issue Date 14/10/2014 Page 17 of 50