Johnson Controls ComBus MS-CQT485-0 User manual

MS-CQT485-0 Manual Documentation Number MS-CQT485-0r1_1910m
Johnson Controls
ComBus Quick Tester
MS-CQT485-0
Documentation Number: MS-CQT485-0r1_1910m
pn#6550

MS-CQT485-0 Manual Documentation Number MS-CQT485-0r1_1910m

Contents
MS-CQT485-0 Manual Documentation Number MS-CQT485-0r1_1910m
i
Section 1: Introduction - Controls & Features ........................1
ComBus Quick Tester.............................................................1
Figure 1 - End & Front View....................................................2
Features..................................................................................1
Introduction .............................................................................2
Section 2: Operation ...................................................................3
Initial Operation ......................................................................3
Flow Chart 1 - Tester & User Operations ...............................4
Table 1 - Voltage Pass Display Sequence .............................5
Section 3: Troubleshooting - Failure Messages ......................7
3.1 24VAC Found ..................................................................7
3.2 Master Found....................................................................7
3.3 Voltage Fail.......................................................................7
Table 2 - Voltage Fail Display Sequence.........................7
Table 3 - Voltage Pass Limits...........................................8
Voltage Fail Checks..........................................................8
Example Voltage Fail Profiles ..........................................9
Table 4 - Profiles.....................................................................9
3.4 Troubleshooting Missing or Bad Devices.......................10
Figure 2 - Split Half Problem Isolation ..................................10
Table 5 - Device Type Display..............................................11
Section 4: Battery Installation .................................................12
Figure 3 - Battery Installation................................................12
Section 5: Specifications..........................................................13
Accessories...........................................................................14

Section 1: Introduction
MS-CQT485-0 Manual Documentation Number MS-CQT485-0r1_1910m
Introduction – Controls & Features
ComBus Quick Tester
Features
•Pluggable 4-Position N2 Bus Connector can accept 3-Position or
4-Position terminal blocks used on Johnson Controls Controllers
•2-Line by 8-Character LCD Display with Power On Backlighting
•Display Scroll-up and Scroll-down buttons
•End of Line Slide Switch for Termination Out/In
•Start button Starts or Stops Automatic Testing
•Power button for On/Off with 5 Minute inactivity timer for Auto
Power Off. Press ½ second for On. Press & Hold for Off.
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Section 1: Introduction
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•N2/MSTP Slide Switch Selects Test Mode (for future MSTP
upgrade)
•Self protected from accidental connection to 24VAC
•Rugged drop resistant case with bright orange color protective
boot uses only 5.5 x 3.4 x 1.4 inches of space.
•Uses two AA alkaline batteries
Introduction
The ComBus Quick Tester is designed to plug into the Johnson
Controls N2 or MSTP bus as a Master Controller. It will test using the
following sequence:
Instrument Test Sequence
1. Check for bus activity, abnormal data state duration such as
24VAC/50/60Hz on data bus or Ref.
2. Check for other Master Controllers on the bus. Only one Master
Controller can be present at a time.
2.1 Master Controllers can be a NCM, Companion, N30 (N2 bus) or
NAE (MSTP bus)
3. Check data bus DC voltages, and retain values for review or
troubleshooting at test end.
4. Poll all device addresses (1 to 255) using N2/Sys91 or MSTP
commands, make internal list of addresses which respond and
identify as either an invalid response or the appropriate N2 or
Sys91 device. (MSTP test mode may vary)
5. Total the number of device addresses which respond and
calculate the sum of all responding addresses for a crosscheck.
If a Fail condition is found during the first 3 tests, testing stops.
Tests 4 and 5 repeat until all addresses have been checked, then the
Device Count is displayed. Use the Scroll-up/down buttons to view.
The total of responding Device Addresses can be checked against
the number of devices which should be present, and the Sum of
responding addresses recorded for future quick checks.
The Device address and Device type can be viewed/checked against
your list of devices which are installed and should be found.
Test 4 can be stopped by pressing and holding the START/STOP
button until Device Address scanning stops.

Section 1: Introduction
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Initial Operation
Before use, install a pair of AA batteries (included) as shown in the
Battery Installation section.
1. Locate the Master Controller for the communications trunk
being tested.
2. Unplug the 4 pin (or 3 pin) Data Bus connection plug from the
Master Controller and plug it into the Quick Tester.
3. Set the N2/MSTP slide switch to test N2 or MSTP bus
devices. The N2/MSTP switch is only read at Power On. In
MSTP mode, initial production units will display “MSTP NO
SUPPORT”. at Power On.
4. Press & release the Power button to turn On.
5. Set the END OF LINE switch to IN if replacing an End Of
Line device (usually only one cable connected to plug), else
set to Out (two cables connected to plug).
6. Press the Start button to begin. To stop before completion,
press and hold the Start/Stop button until halted.
7. If a failure message is displayed, “”24VAC Found”, “Master
Found” or “Voltage Fail”, troubleshoot as in Section 3.
8. When “Voltage Pass” is displayed, “Hit up down key”,
automatic testing is done. Check results.
9. Press & release the scroll-down button to sequence through
results. Compare the Device Count found to the number of
devices installed. If equal, and the “Add. Sum” matches the
value specified for the system, testing is complete except for
recording system values for future reference.
10. If not equal, see Troubleshoot Missing or Bad Devices.
Continued next page.

Section 2: Operations
MS-CQT485-0 Manual Documentation Number MS-CQT485-0r1_1910m
Tester & User Operations
Flow Chart 1 - Tester & User Operations
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Section 2: Operations
MS-CQT485-0 Manual Documentation Number MS-CQT485-0r1_1910m
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When the Tester stops testing, User Checks are needed to complete Testing
using the up/down keys.
The User must compare the device count found to actual number of devices
present, and the Add. Sum to the Engineering Check Sum provided for the
installation being tested. See Table 1 for the Display Sequence.
If the Device Count is correct then there are no missing devices.
If the Address Sum is not correct, but the Device Count is correct,
then one or more device addresses is not set according to the
Engineering Check Sum specified. See Section 3, Troubleshooting
Missing or Bad Devices.
Table 1 – Display Sequence
# Display Action Comments
1 Hit up down
key D = Data Bus
2 Add. Sum
XXXXX
XXXXX = Sum Sum of all
addresses
found
3 +=x.xxV
-=x.xxV
x.xx = value +D Line to REF
-D Line to REF
4 Bias =
+X.XX
x.xx = value +D to –D
5 XXX ZZZ
XXX ZZZ
XXX =
Address
ZZZ = Dev
Type Code
If device count
> 0 then show
first 2
5 XXX ZZZ
XXX ZZZ Repeat in sets
of 2 until all
shown
6 Devices=
0000
Show count of
devices found
2 Add. Sum Repeat #2
+D is Data bus plus (with N2 bus = N2+) MSTP Future
-D is Data bus minus (with N2 bus = N2-) MSTP Future

Section 3: Troubleshooting
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Troubleshooting - Failure Messages
3.1 – 24VAC Found
1. Unplug the connector from the Tester verify that the 24VAC
power connection and Data bus connections are not
swapped.
2. Use a Multimeter and check for 24VAC between the +D line
and –D line connection, then between the +D and REF, and
between the –D and the REF.
3. If no AC, possibly some device on the bus has the REF line
swapped. Split the trunk and troubleshoot each half
separately.
3.2 – Master Found
1. Check for a Master (NCM, N30, NAE, Companion) connected
and polling.
2. If necessary, split the trunk and troubleshoot each half
separately.
3.3 – Voltage Fail
Voltage Fail means that abnormal DC levels on the bus have been
measured.
The ComBus Quick Tester checks for normal values on +D and -D to
REF (Common Mode Reference), and the difference between +D and
-D (known as Bias).
Table 2 – Display Sequence
# Display Action
1 Hit up down
key
2 +=x.xxV
-=x.xxV
3 Bias =
+X.XX

Section 3: Troubleshooting
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Table 3 – Voltage Pass Limits.
# Voltage
Pass Lower Limit Upper Limit Parameter
D=Data Bus
2 + = 2.45V 3.00V +D to REF
2 - = 1.90V 2.54 -D to REF
3 Bias = +0.38 +0.92 +D to -D
+D is Data bus plus (with N2 bus = N2+) MSTP future
-D is Data bus minus (with N2 bus = N2-)
Voltage Fail Checks
1. Check that End of Line termination is set correctly.
2. Compare Lower Limit values, low values can indicate a data
line shorted to another, or to REF, or reversed at an End of
Line device.
3. See Voltage Fail Example Profiles
The DC levels between data transmissions on each line will vary
depending on how many devices are on the bus, since each device
loads it, changes the bias. The bias voltage for all devices on the bus
establishes the no-signal state between data transmissions when all
devices are tri-stated. DC bias is needed so all devices on the bus
are able to recognize the start of data without errors or retries.
See Example Voltage Fail Profiles – next page.