Delta Controls 2HT - Manual (Page 16)

002522-2HT 180210.doc 16
OPTIONS
Mounting
Stainless steel wall and pipe clamps are available as an optional way of
mounting the unit.
Display / Configurator
The D-CAL configurator / display may be ordered with the transmitter or
retrofit at a later date, without compromise to the certifications. This unit is
not loop powered and can only be used with the Delta Controls HT range of
SMART Transmitters.
SPARES
Lid 'O' Ring
:- Spares No. 155042
Display 'O' Ring :- Spares No. 155043
Display Overlay :- Spares No. 9020311
Lid ( Free Blank ) :- Spares No. 9420004
Lid ( Free Windowed ) :- Spares No. 9400123
Display Assembly :- Spares No. 9400124
MAINTENANCE
The unit requires no maintenance as standard, but it is recommended that all cable terminals be
checked for tightness at standard site maintenance intervals. Please note that all of the circuit boards
within the unit are protected against water damage so
it is unnecessary to apply any other form of
protection, as this may void the products warranty.
RE-CALIBRATION
The 2HT series instruments are designed for long and stable lifetime operation.
The nature of a combined analogue / digital instrument such as this, is that the Analogue to Digital
Converter that processes the sensor input measures the total permitted pressure range of the
instrument, irrespective of the chosen output of the 4 to 20 mA range. Changes in the selected
4 to 20 mA output are made against the stored, compensated values of pressure conversion.
From time to time, however, it will be necessary to check, and, if required, trim the scaling of the A-D
converter against a local pressure standard.
The method used by the 2HT series, assumes that the two most important calibration points for the
chosen application are the Lower and Upper Range Values set for the 4 to 20 mA output. These, not
the instrument’s zero and nominal Upper Range Limit, are the values to be applied to the instrument
when trimming the ADC.
Apparatus Needed
A accurate pressure supply (+/- 0.03% of value)
A Delta D-CAL Communicator (as the procedure requires a Device Specific command, only software
versions 5.00 and later may be trimmed via HART® )
Method
Apply a pressure value equal to the instrument’s selected Lower Range Value. In the ACCESS2 menu
of the D-CAL, go to {TRIM LRV}[SELECT]
{HIT SAVE} will be displayed, there are two choices :-
[SELECT] or [CHANGE] To abort and return to the {TRIM LRV} menu
[[SELECT]]
Press and hold for two seconds to store the ADC offset value, {SAVED} will be
displayed to show that the command is successful.
Now apply a pressure value equal to the instrument’s selected Upper Range Value, and repeat the
above sequence, with {TRIM URV}.
The ADC is then set to the site standard. For full explanation of the D-CAL functions, see the D-CAL
Configurator Manual.