Optimum Operating Temperature - Honeywell SLG 700 User Manual

3.2.8 Optimum Operating Temperature

Overview
3.2.8.1
When you deviate from reference conditions some of the SLG720/726 specifications can be
sub-optimal and in particular the upper and lower blocking distances may need to be
increased at the operating temperature extremes. The document outlines a few options to
maintain best operation at temperature.
Transmitter Behavior at Temperature
3.2.8.2
All of the PCBAs except the display of the SmartLine Guided Wave Radar (GWR) Level
Transmitter are rated to operate within a temperature range from -40°C to 85°C. The display
is rated to operate to a maximum of 70°C. Also note that for intrinsically safe (IS)
installations the maximum allowable operating temperature for all SmartLine transmitters is
70°C. At high temperatures the pulse may change slightly from its ambient shape.
A consequence is that a field background obtained at the lower temperature reference
conditions may not be accurate and cause incorrect processing of the data, especially at the
start of the probe.
The purpose of this note is to outline recommendations when operating the GWR level
transmitter with electronics temperature above 60°C or below -20°C.
Note if the transmitter electronics is above 60°C because of radiative heating from the sun it
may be possible to reduce the temperature below 60°C by installing a shield to shade the
transmitter.
Reconfiguration Instructions
3.2.8.3
Depending on the application and customer preferences, there are a number of options for
optimizing measurement performance at temperature effects when the level is near the
process connector.
1. Turn off full tank detection* especially when the dielectric constant is less than 12. Refer
to the SLG 700 HART option manual 34-SL-25-06 or the SLG 700 FOUNDATION
Fieldbus manual 34-SL-25-07. This disables the software from detecting a reflection
close to the process connector inside the blocking distances.
2. Enable Dynamic Background updating. This feature allows the sensor to automatically
update the background echo profile every 10°C or every few hours as long as the level is
reliably detected and of sufficient distance from the process connector. If the level is
consistently within 30cm of the process connector however, no update can be performed.
Note that the updated backgrounds are permanently stored on the sensor and are reloaded
after a reset.
3. Options 1 and 2 above should always take care of any temperature effects but it can also
help if a field or obstacle background at or near the operating temperature of the device
can be taken. Backgrounds can be taken using the Honeywell DTM, the local display, or
the supported handhelds. The DTM instructions can be found in the SLG 700 HART
option manual 34-SL-25-06.
Revision 7
SLG 700 SmartLine Level Transmitter User's Manual
Page 59