To confirm that the scale is acceptable, use the “Leak” option in the 4–20 mA Test menu.
Simulate leaks at various locations, and verify that the output is as expected with the
equipment or instrument connected to the TTDM 4–20 output port.
Note: The maximum current output can be calibrated using trimpot R7 on the 4–20 mA
circuit board (8 on foldout).
Serial Port
The external communications port is configured for use as either RS-232 or RS-485. The
factory default is RS-232 full-duplex with no hardware handshaking.
This is suitable for connection to a remote host PC, laptop, serial printer, or modem. With
the appropriate cable and standard terminal software, a PC can receive time, communica-
tions, and Events History data.
One of the simplest but most important uses of the serial port is obtaining a printout of
the Events History log with a serial printer, or a PC with communications software.
Contact your Raychem TraceTek representative for additional information to assist in con-
necting and configuring for serial port communications.
Connection Details
The illustration below shows the pinouts/terminals for the alarm relays, 4–20 mA port,
and RS-232/485 serial port. (labeled EXT COM PORT on the motherboard)
+51SO
1
PL
RS-485 EXT XMTRS
J10
PL
RS-232/485 EXT COM PORT
J13
PL
4-20MA OUT PORT
J2
SERVICE RELAY
5A 250V
J6
ALARM RELAY
5A 250V
J25
TROUBLE RELAY
5A 250V
J9
1
1
1
1
1
ICOM 485+ 485–
1
2
3
4
RX/A TX/B RTS CTS +5V GND
5
6
7
8
9
10
IRTN IOUT +V +VRTN
11
12
13
14
NC NO COM NC NO COM
15
16
17
18
19
20
NC NO COM NC NO COM
21
22
23
24
25
26
NC NO COM NC NO COM
27
28
29
30
31
32
4–20 mA Current Transmitter
The TTDM adjusts its 4–20 mA output based on the leak detection status as detailed below.
Fault conditions:
Output (mA)
Description
0
Electronic fault or loss of power
1.00
Fault—communications between SI and UI boards
2.00
Fault—cable break
3.00
Fault—cable damage (loop imbalance)
3.50
Service Required alarm
Normal conditions and leaks:
4.00
System normal
5.00 - 20.00
Leak; value scaled to indicate location of leak
Testing
When external equipment is connected to the TTDM 4–20 mA output port, the current
loop can be tested using the “4–20 mA Test” series under the Self-Test Menu. Before
doing so, confirm that all connections have been made, including 24 Vdc to TTDM
terminals 13 and 14. To conduct the 4–20 port tests, make the following menu selections,
beginning from the Main Menu: “View/Edit Settings,” “Self-Test Menu,” “4–20 mA Test.”
The entries in the 4–20 mA Test Menu are:
Electronics Fault
SI Comm Error
Cable Break
Loop Imbalance
Service Req’d
System Normal
Leak (a submenu prompts for a location to simulate)
20 mA Val
All but the last entry simulate the conditions noted; the TTDM changes its current output to that
designated for the condition selected (for example, 3.50 mA for a Service Required alarm).
Adjusting the Scale
Default value for the upper bound (i.e. the location that would result in the maximum cur-
rent output of 20 mA) is 5000 ft. (1500 m). To change the scale, select “20 mA Val” at the
bottom of the “4–20 mA Test” menu. Then enter a new upper bound to provide a reasonable
scale for your system.
Important: The upper bound must be greater than the Test Length (which the TTDM
displays in the System Status screen).
30
31
Appendix 4 - Interface Details
