Cooper Instruments & Systems DFI 1650 Multi-Channel Digital Force Indicator - Manual (Page 27)

CF 66 21 Rev. C 2/05
To change whether the channel’s track, peak or valley data value is displayed on power-up, use the channel’s
“OPERATION->POWER->ON SOURCE” menu item.
9.0 LIMITS
9.1 Understanding Limits, Set Points and Return Points
Limits are signal levels at which some action (such as a light to come on or go out, or a switch to close) is desired
to take place. The point at which this action takes place is the SET POINT. The RETURN POINT is the point at
which the action that took place at the SET POINT returns to its original state.
If the SET POINT and RETURN POINT are identical and the signal level is changing slowly near these points,
“chatter” may result and the limit rapidly energizes and de-energizes. To keep this from happening, we can specify
the SET POINT at which the action would occur as well as the RETURN POINT where we want the action to
cease. If the amount of “dead band” between these two values is more than the expected noise, the desired action
will take place only once. The SET POINT and the RETURN POINT should always be separated to insure that
small amounts of noise on the signal will not become a problem.
A good general rule for SET POINT and RETURN POINT values is that they should be separated by at least one
percent of the full-scale value.
9.2 Limit Operation
9.2.1 Actions When Activated
When Limits 1, 2, 3 or 4 are activated, the following actions occur:
• The front panel light for the limit will illuminate.
• The corresponding open-collector Limit Output pin on the System connector will be connected to the DGND
(Digital Ground) pin.
• If a Relay Output channel is installed, the relay for the limit will activate.
A Relay Output channel can be installed for Limits 5, 6, 7 and 8. When these limits are activated, the following
actions occur:
• If the display is monitoring the channel of this Relay Output channel, the display will indicate the status of these
limits.
• On a DFI SC3004, the front panel light for the limit will illuminate.
• The relay for the limit on this Relay Output channel will activate.
A Relay Output channel can be installed for Limits 9, 10, 11 and 12. When these limits are activated, the following
actions occur:
• If the Relay Output channel is displayed, the display will indicate the status of these limits.
• The relay for the limit on this Relay Output channel will activate
A Relay Output channel can be installed for Limits 13, 14, 15 and 16. When these limits are activated, the following
actions occur:
• If the Relay Output channel is displayed, the display will indicate the status of these limits.
• The relay for the limit on this Relay Output channel will activate.
9.2.2 Scan Time
The “scan time” or update rate of the limits depends on how many channels are installed in the instrument. To
determine the scan time of the limits for your particular instrument, see “SCAN TIME Menu Item” in Section 6.2.3.
9.3 Limit Menus
9.3.1 Overview
There are four, eight, twelve or sixteen Limit menus depending on how many Relay Output channels are installed in
the instrument. These menus determine the operation of each of the limits.