B1556 Meter Pulse Isolator Manual - Barnett Engineering Ltd

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Prepared by:
B.T. Barnett, P.Eng.
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November 13, 1992

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GENERAL DESCRIPTION ................1
CIRCUIT DESCRIPTION .................1
INSTALLATION ........................2
PARTS LIST ............................3
DRAWINGS ............................4

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The B1556 meter pulse isolator provides an isolation/driver interface between a process
meter pulse signal and externally connected equipment. The input is a high impedance
port which presents negligible loading to the signal source; the outputs are optically
isolated drivers that reproduce the waveform that appears at the input.
Two identical outputs are provided - either or both can be used as required.
The circuit is contained on a single PC board which can be mounted in snap-track or on
standoffs with the 4 holes provided. Field wiring connections are via a compression screw
terminal strip.
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-refer to drawing B1556-S01
Power to the circuit is +24 VDC which is connected to TB-1 and TB1-2. A 1/4 Amp fuse on
the incoming 24 volt line protects the circuit. Two 12 volt regulators are used to provide
the operating voltage for the isolator. Regulator U2 provides the voltage for the input and
driver side of the opto-isolators; regulator U3 provides the voltage for the output side of
the isolators. In this way the output and input sections are isolated in the event of a foreign
voltage appearing on the output. Damage to the circuit from events at the output will be
limited to the output sections and will not damage the input or the connected equipment.
An LED indicator shows when power is present.
The input accepts a 12 volt, ground referenced, signal at TB-1. The network of components
that pass the signal provide transient and voltage violation protection for the input buffers.
The DC input impedance is 100k6. The input signal is split and then driven into transistors
Q1 and Q2. Q2 drives the two isolators in phase with the input signal while Q1 drives the
signal indicator out of phase with the input signal to give the correction indication of
activity.
While the isolators, U4 and U5, are driven by Q2 their output transistor is saturated to
become a closed circuit. Switch settings are available to condition this closure to appear as
several formats at the output pins.
The settings are:
a. In-phase driver with 1k6 output impedance (as shipped)
- all switches in the closed position
b. In phase driver with open collector
- SW1-B and SW1-D open
If this configuration is used an external pullup must be used.
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c. Inverted driver with emitter drive
- all switches open
If this configuration is used the + signal line must be tied to an external voltage
source and a pulldown connected to the - signal line.
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After the module has been mounted, the connections are made as shown in drawing B1556-
D03. Either output can be used for single signal applications.
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Resistors - values are in ohms, 5% tolerance 1/4 Watt
R1 4.7k
R2 2.2k
R3 470
R4 100k
R5 1k
R6 1k
R7 470
R8 1k
R9 1k
R10 1M
R11 1M
Capacitors - values are in microfarads unless noted
C1 1000 35V axial aluminum electrolytic
C2 33pf 50V axial ceramic
C3 33pf 50V axial ceramic
C4 .1 50V axial ceramic
C5 .1 50V axial ceramic
C6 .1 50V axial ceramic
Semiconductors
U1
U2
U3
U4
U5
Q1
Q2
4093B quad NAND gate
7812 regulator
78L12 regulator
4N25 opto-isolator
4N25 opto-isolator
MPS6560
MPS6560
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D1-D7 1N4005 diode
D8, D9 FLV117 LED
MOV1
07K35
Other components
F1
SW1
TB1
PCB
1/4 Amp
4 position DIPswitch
WIBA 8281 - 8 position
B1556
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'5$:,1*6
B1556-S01
B1556-L02
B1556-D03
SCHEMATIC
COMPONENT LAYOUT
CONNECTION DIAGRAM
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D1
1N4005
D7
1N4005
D2
1N4005
8
9
U1
10
12
13
U1
11
5
6
U1
1
2
4
U1
3
U4
U5
D3
1N4005
D4
1N4005
D5
1N4005
D6
1N4005
6
3
4 5 1 8
2 7
+24 VDC
GND
SIGNAL IN
SIGNAL COMMON
TB1
1
TB1
2
TB1
TB1
F1
1/4 A
C4
.1
3
4
+12
MOV1
C1
1000
1
R3
470
C2 C3
33pf 33pf
U2
7812
+12
C5
.1
U3
78L12
2
3
C6
.1
R4
100K
+12I
R1
4.7K
+12
R6
1K
D8
FLV117
SIGNAL
R7
470
Q1
MPS6560
+12
R5
1K
D9
FLV117
POWER
R2
2.2K
Q2
MPS6560
+12
+12I
+12I
R8
1K
SW1-B
4N25
SW1-A
R9
1K
SW1-D
4N25
SW1-C
+12I
5
6
R11
1M
+12I
7
8
R10
1M
TB1
TB1
TB1
TB1
SIGNAL A OUT +
SIGNAL B OUT -
SIGNAL B OUT +
SIGNAL B OUT -

125
36
36
36
36
36
U2
SIGNAL
POWER
R5 36
R6 36
R7 36
36 36 36
36 36 36
R2 36
R1 36
C5
36 36
36
36
36
BARNETT ENGINEERING LTD.
METER PULSE ISOLATOR
B1556
D8
SW1
Q1
Q2
43
36
36
36
36
36
36
36
36
36
36
D9
36 R10 36
36
36
U5
36 36
36 R11 36
36
36
U4
U1
36
36
36
36
36 36
36
36
36
36
36
36
36 36
D7 43
U3 36 36 36
GND A
PULLUP A
GND B
PULLUP B
36
36
36
36
36
R8 36
R9 36
R4 36
36 36 C3
36
43
43
43
43
D5 43
D6 43
D3 43
D4 43
43 D1 43
43
R3 36
MOV1 36
C6
36 36
36 C2
D2 43
36
36
36
36
36
36
36 36
MADE IN CANADA
-OUT B
+OUT B
-OUT A
+OUT A
- SIG
+ SIG
GND
+24 V
C4
36 36
63
63
63
63
63
63
63
63
TB1
125
C1
+
36 36
81 81
81
81
F1
1/4 AMP
125
125