13
Signet 8900 Multi-Parameter
6.2 Digital
(S
3
L) Input wiring
•
The maximum cable length of the digital (S
3
L) bus varies depending on the types of sensors connected and the size of the
conductors in the cable. For best results, determine the maximum cable length for the system before routing cables.
•
Frequency input signals from fl ow sensors are not part of the digital bus, so they do not impact the cabling calculations. Follow the
maximum cable specifi cations published in the fl ow sensor literature.
•
The digital (S
3
L) bus can be connected to two sets of terminals on the 8900. Divide digital (S
3
L) sensors between the two points to
stay within the limits defi ned here.
•
There are several methods that can help route the digital cables and remain within the distance limitations. The following pages
provide general wiring concepts for different systems.
* 2551/2552 Magmeter and the 8900
The 2551 or 2552 Magmeter may require up to 15 mA per unit under some conditions. Special attention must be paid to power
requirements when more than three 2551 or 2552 Magmeters are connected to the 8900.
To ensure that Magmeters receive suffi cient power, Signet recommends minimizing other power requirements in the 8900 by doing at
least ONE of the following:
• Select solid state relay cards instead of dry contact relays.
• Select Passive analog output cards instead of Active.
• Select the DC power supply card instead of the AC card.
Any one of these measures will insure that the 8900 has suffi cient power available to support up to six 2551 or 2552 Magmeters.
Multi-drop
Daisy-chain
3-8900.621C
I/O Module 3-8900.401-X
1
2
3
4
5
6
7
8
9
10
11
12
13
14
+5VDC (Black)
Freq. Input (Red)
GND (Shield)
+5VDC (Black)
Freq. Input 2 (Red)
S L (Red)
GND (White/Shield)
+5VDC (Black)
S L (Red)
GND (White/Shield)
3
3
Analog Output 1
Analog Output 2
(if applicable)
(if applicable)
Frequency
Input
1
Frequency
Input 2
OR
S3L
Input
2
S3L
Input
1
+
-
+
-
S³L
Branch 1
S³L
Branch 2
How to Wire Digital (S
3
L) Sensors
1. Tie all red wires together.
2. Tie all white wires together.
3. Tie all black wires together.
4. Tie cable shield to white GND wire at one end only for added protection from noise interference.
Notes:
•
Some installations may require connecting the cable shield to Earth ground to overcome noise interference.
•
Terminals 4-7 may be used as Freq Input 2 or as digital (S
3
L) Input 2, but not both.
•
For best EMI fi ltering, divide digital sensors between S
3
L Input 1 and S
3
L Input 2 if Input 2 is not required for Frequency input.
•
Daisy-chain or multi-drop wiring for digital (S
3
L) devices will reduce the number of separate digital signal lines that must be
connected to the 8900 I/O Module.
•
Ferrules are recommended when connecting multiple digital (S
3
L) devices to a single set of terminals.
•
In a "Daisy-Chain" pattern, the wires from each sensor are spliced to the matching wire of the adjacent sensor.
•
In a "Multi-Drop" pattern, the wires from each sensor are spliced to a common set of wires from the 8900.
•
Wiring methods can be mixed in any convenient design when connecting digital (S
3
L) devices. See the wiring charts on the
following pages for a variety of wiring options.
• The
specifi c type of sensors on a branch of the digital (S
3
L) bus determine the current requirements, and the maximum cable
length for the branch. See section 6.2.1 for details.
