Section 5
Page 5 - 14
HA243821
Issue 5 Mar 98
MODEL 346 INSTALLATION AND OPERATION MANUAL
5.5 RANGE MAGNIFY
5.5.1 INTRODUCTION
When signalled by an internal trigger (section 3.4) or when manually selected from the operator menu (section
3.3), this feature changes the ranges of all selected channels. Range magnify is independent of the History
Magnify feature described above, except in that the Mag. Centre’ function (described below) applies to both.
The term ‘magnification factor’ is used for the number that determines how much and in which direction the range
will be changed. A factor of greater than 1.0 expands the range, so that a smaller part of the range appears on the
chart, but with more detail. A factor of less than 1 contracts the range giving less detail.
MAGNIFICATION CENTRE (MEASURING CHANNELS)
The ‘Mag center’ value is set up in the channel configuration pages for each relevant channel, and providing that
it lies within the channel’s range, this value acts as a centre point for the magnified range.
EXAMPLE
The normal input range for a channel is 0 to 1200 ˚C; the magnification factor is set to 6; the magnification centre
is set to 900 ˚C.With the above settings, the magnified range (normal range divided by the magnification factor) is
1200 / 6 = 200 ˚C. The range (
±
100 ˚C) is centred about the centre value, giving a new scale of 900
±
100 ˚C i.e.
800 to 1000 ˚C.
If the centre value lies outside the normal range, it is ignored and the magnified range is centred about the process
value existing at the time of Range Magnify initiation. In such a situation, on-chart printing is assured, but the
resulting scale end values can be non-integer.
MAGNIFICATION CENTRE CONFIGURATION (MEASURING CHANNELS)
The Magnification display page appears after the ‘Set Chart Range’ display page in the channel configuration
menu (section 4.8)
MAGNIFICATION CENTRE (DERIVED CHANNELS)
The operation of the Magnification Centre feature for derived channels is the same as that described above for
measuring channels, with the following exception:
The high and low range inputs in the derived channel configuration are used to enable / disable the Magnification
Centre function. The function is active when the high and low range are set above and below the centre value
respectively. The feature is disabled if both low and high range values are set either above or below the centre
value.
MAGNIFICATION CENTRE CONFIGURATION (DERIVED CHANNELS)
The ‘Range High’, ‘Range Low’ and ‘Mag Center’ display pages appear after the ‘Enter Descriptor String’ page in
the derived configuration (section 5.5.3)
