Measurement Computing DBK Part 2 - Manual (Page 193)

Hardware Setup
Connecting Thermocouples
Each DBK100/D and DBK100/T can accept up to 14 mini-TC plugs in its channels 0 through 13. All
channels have the same level of functionality. Up to four DBK/100 units can be attached to a single
channel of a DBK101 hub. With its 8 channels, a total of 32 DBK100 units can be connected to a single
DBK101.
o
14 thermocouples can be connected to each DBK100/T or DBK100/D.
o
Up to four DBK100/T or DBK100/D units can be connected to a each DBK101 channel.
o
DBK101 has 8 channels. Thus 32 DBK100 units can be connected to a DBK101. With 14
thermocouples possible per DBK100 unit, 448 thermocouple connections are possible for one
DBK101 hub.
o
Two DBK101 hubs can be connected to a DaqBook/2000 Series unit. When 2 hubs are used the
system can have up to 896 thermocouples (448 x 2).
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
DBK Option Cards and Module 907994 DBK100 Series pg. 5
R Black Red
B Gray Red
Red (-) connects
to Channel Low
The (+) color,
see table,
connects to
Channel High
DBK100/T users need to be aware that mini-TC plugs are type-specific. 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 DBK100/T 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 employing one or both of the following practices:
o
using shielded thermocouples
o
averaging readings
DBK101 includes a jack labeled “ACOM.” The jack is typically used for connecting the shield of a
shielded thermocouple to the DBK101 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 DBK101 hub, 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.