Measurement Computing DBK Part 2 - Manual (Page 177)

DBK Option Cards and Module 907492 DBK90 pg. 3
Hardware Setup
Connecting DBK90 Modules to Thermocouples
The DBK90 accepts up to 56 mini-TC plugs in its channels 0 through 55. All channels have the same level
of functionality.
Thermocouple wire is standardized, color-coded, and polarized, as noted in the following table.
Thermocouple Standards
T/C
Type
(+) Lead to
Channel High
(-) Lead to
Channel Low
J White Red
K Yellow Red
T Blue Red
E Violet Red
N28 Orange Red
N14 Orange Red
S Black Red
R Black Red
B Gray Red
Mini-TC plugs are type-specific, and for best measurement operation the plug TC type should match the
wire TC type. If necessary, copper/copper (Type U) plugs may be used, but measurement stability will be
slightly degraded. Mini-TC plugs are polarized as well, and it is critical for proper measurement operation
that this polarity be followed when connecting the thermocouple wire. Once wired, the TC plugs will only
mate into the DBK90’s connectors in one orientation, ensuring a correct connection.
It should be noted that thermocouples output very small voltages and that long thermocouple leads can
pickup a large amount of noise. If desired, noise reduction can be achieved through the use of shielded
thermocouples and/or averaging.
You can minimize the effect of noise by (1) using shielded thermocouples,
(2) averaging readings, or (3) employing both of these practices.
Each DBK90 includes a jack labeled “ACOM.” The jack is typically used for connecting the shield of a
shielded thermocouple to the DBK90’s analog common. When this connection is made the shield at the
other end of the thermocouple is left unconnected.
If a thermocouple shield is connected to the DBK90 module, leave the shield
unconnected at the other end of the thermocouple. Connecting the shield to common
at both ends will result in a ground loop.
The jack accepts a removable 2mm banana plug for ease of making and breaking the analog common
connection. The 2mm banana plug that is shipped with the product is part number 5936-0 from Pomona®
Electronics.
The ACOM connector is a 2mm banana jack. To ensure a good connection that will not
damage the jack, use a Pomona® Electronics 2mm banana plug (p/n 5936-0). The use of a
different plug (including a 0.08 inch tip type) may damage the ACOM jack.
Reference Note:
In regard to automotive applications, refer to the upcoming section entitled, Vehicle Testing.
The section begins on page 9.
Red (-) connects
to Channel Low
The (+) color,
see table,
connects to
Channel High