Comet MS6D, Инструкция по эксплуатации, Страница: 47 / 56

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8. RECOMMENDATION FOR OPERATION AND MAINTENANCE
8.1.1 Operation of data logger in various applications
Before application it is necessary to consider if data logger is suitable for required purpose, adjust
optimal configuration and create instructions for its periodical metrological and functional verifications.
Unsuitable and hazard applications: data logger is not design for applications, where failure of
operation could cause endanger of health or function of other device supporting life functions. In
applications, where failure of data logger could cause loss on property, it is recommended to amend
system of independent indication device to monitor this state and avoid damages. It concerns especially
control and indication outputs of data loggers. In critical applications it is suitable to power data logger
from backed-up sources (UPS) dimensioned to required operation without mains power. Furthermore
critical can be data logger connection to power itself. It is not suitable to power both data logger and
critical device
–
e.g. freezing box
–
to one fuse. If fuse is disconnected, then neither data logger nor
monitored device is working. . In such applications it is useful to set inverse behavior of output
ALARM OUT, when status without alarm is signaled by closed relay.
Location of temperature transducers: locate them to places with sufficient airflow and where most
critical point is supposed (in accordance with application requirements). Transducer must be located
sufficiently inside of measured room or be connected to, to avoid thermal influence of leading wires to
measured temperature. In monitoring of temperature in air-conditioned room, do not locate transducer
to direct flow of air conditioning unit. E.g. at large chamber refrigerators can be temperature profile
ver
y inhomogeneous, deviations can reach up to 10 °C.
Location of humidity transducers: in measuring of humidity in refrigeration boxes without additional
humidity stabilization, strong changes of humidity can occur in switching on/off the refrigeration (up to
tens of % RH) even though mean RH value is stable.
Optimum data logger operation: it depends on particular application. Important is the setting of logging
and alarm parameters. It is necessary to take into account the memory capacity of data logger and
frequency of data transfer to the computer. Select logging mode depending on preferable way of data
management. If newest data are preferred select cyclic mode, if oldest data are preferred, select
noncyclic mode. Further more consider if data will be erased from data logger after data transfer to the
computer. In case data will be erased, then a long-term record is not stored in one file and it is not
possible to identify eventual failures. In case memory is not erased, then data transfer duration to
computer can be a problem. If there are problems with data logger, it is recommended not to erase data.
Alarm delay and hysteresis settings are very important.
8.1.2 Recommendation for metrological verification
Metrological verification is performed in accordance with application requirements specified by the
user. One year the manufacturer recommends periodical verification.
Notice: accuracy of data logger input means accuracy of input itself without probes.
In verification of thermocouple inputs it is necessary to take into account that cold end compensation is
perform inside of data logger, where temperature is mostly slightly higher than ambient temperature on
the outer connector. Best way is verification together with connected thermocouple.
8.1.3 Recommendation for periodical verification
Manufacturer recommends periodical verification of the system yearly. Interval and range of verification
depends on the application. In stationary installations following verification is recommended:
1. Metrological verification
2. Regular overhaul in intervals accordingly to corresponding standards
3. Evaluation of all problems from the last verification
4. Visual inspection of data logger
5. Functional verification of data logger (functions used in application):
A) verification of data transfer to computer
B) verification of alarms
–
change input value to activate alarm and check on display and also
in external audio indication (if used)