Function Input Pins; Overview; Example; Limit Output Pins - Honeywell SC Series Installation Instructions Manual

Signal Conditioning, Self Calibrating Digital Indicators

5.3 Function Input Pins

5.3.1 Overview

To use a Function Input pin (9, 10, 11 or 21), connect it to the
DGND (pin 19) momentarily. This can be accomplished by a
push button switch, relay contact closure, or PLC output.
Usually, the Function Input pins perform the default actions de-
scribed in the "System Connector Pinout" on page 17. However,
a SensoCode program running on a Mathematics Virtual Channel
may replace these default actions. Consult the Customer Infor-
mation Sheet included with your instrument for details.

5.3.2. Example

For example, assume that you wish to use Function Input #3 to
tare all channels in the instrument simultaneously. Connect a
push-button switch as shown below.

Figure 5-1: Function Input Example

SYSTEM CONNECTOR
DESIGNATION PIN
FUNCTION INPUT 3 21
DIGITAL GROUND 19

5.4 Limit Output Pins

5.4.1 Overview
An open-collector output is a transistor logic output that can be
used to control dc loads, drive opto-isolators or relays, or inter-
face directly to logic circuitry. They act very much like switches:
low resistance when turned on and high resistance when turned
off. You can use them as you would a dry relay contact, with the
following restrictions:
• The voltage applied must be dc
• The polarity of the dc voltage must be observed
• Maximum voltage: 50 Vdc
• Maximum power: 2.0 W
When Limits 1, 2, 3, or 4 are activated, the corresponding open-
collector Limit Output pin on the System connector will be con-
nected to the DGND (Digital Ground) pin. However, a SensoCode
program running on a Mathematics Virtual Channel may override
this behavior. Consult the Customer Information Sheet included
with your instrument for details.
18 Honeywell Sensing and Control
5.4.2 Example
For example, assume that a remote indicator is to be lighted
when Limit 1 is activated. An external 24 Vdc power supply con-
nects to the indicator.
When Limit 1 is deactivated, there is high resistance between
the Limit 1 Output pin and the DGND (Digital Ground) pin; little
current flows in the circuit and the light is off. When Limit 1 is
activated, there is low resistance between the Limit 1 Output pin
and the DGND (Digital Ground) pin; the light turns on.
The resistor limits the current flowing in the circuit when the light
is lighted to 48 mA. According to Ohm's Law:
Lights or other indicators have voltage, current, and/or power rat-
ings that must be observed in order to avoid damaging them.
PUSH-BUTTON
SWITCH

Figure 5-2: Open-Collector Output Example

SYSTEM CONNECTOR
48 mA =
500 OHM
RESISTOR
DESIGNATION PIN
LIMIT 1 OUTPUT 14
DIGITAL GROUND 19
008-0608-00
Rev. G,
V
I =
R
24 V
500 Ω
INDICATOR LIGHT
24 Vdc
POWER SUPPLY
(+)
(-)