Measurement DBK84 User Manual

DBK84 14-Channel Thermocouple Module

Overview …… 1
Hardware Setup …… 2

Module Connection …… 2
Open Thermocouple Detection …… 3
Module Configuration …… 4
DaqBook/100 Series & /200 Series and DaqBoard [ISA type] Configuration …… 5
DaqBook/2000 Series and DaqBoard/2000 Series Configuration …… 5

Software Setup …… 6
Using a Temperature Calibrator …… 7
DBK84 – Specifications …… 8

Reference Notes:

o Chapter 2 includes pinouts for P1, P2, P3, and P4. Refer to pinouts applicable to

your system, as needed.

o In regard to calculating system power requirements, refer to DBK Basics located near

the front of this manual.

Overview

The DBK84 is used in temperature measurement applications and provides connections for 14
thermocouples through convenient mini-TC connectors.

The DBK84 features on-board cold junction compensation (CJC) for direct measurement of type J, K, T, E,
N28, N14, S, R, and B thermocouples. The following table provides the temperature range for each of
these thermocouple types.

Thermocouple Temperature Ranges
T/C Type J K T E N28 N14 S R B
Temperature
Range °C
Temperature
Range °F

-200 to
760

-328 to
1400

-200 to
1200

-328 to
2192

-200 to
400

-328 to
752

-270 to
650

-454 to
1202

-270 to
400

-454 to
752

0 to
1300

32 to
2372

-50 to
1768

-58 to
3214

-50 to
1768

-58 to
3214

50 to
1780

122 to
3236

Up to fourteen external thermocouples can be connected to the DBK84 module. Channels 1 through 7 are
used for the first seven thermocouples, and channels 9 through 15 are used for the second set of seven.

Note: DBK84 has two on-board CJCs. They are measured on channels 0 and 8.
In addition to thermocouple measurements, each input channel can be configured for a fixed voltage gain

of 100. When in this mode, voltage can be measured in the range of ±100 mV, or ±50 mV, depending on
the type of Daq device being used.

Up to sixteen DBK84 modules can be attached to a single LogBook or Daq device, providing up to 224
temperature channels.

DBK Option Cards and Module 989494 DBK84 pg. 1

Hardware Setup

Module Connection

The DBK84 accepts up to 14 mini-TC plugs in its channels 1 through 7 and 9 through 15. All channels
have the same level of functionality.

Thermocouple wire is standardized, color-coded, and polarized, as noted in the following table.

In comparison to typical DBK options, the DBK84 demands significant power from the
system’s ±15 V power supplies. It is important that you calculate your system’s power
demand, as you may need to add auxiliary power supplies. For additional information
refer to Power Requirements in the DBK Basics section.

Thermocouple Standards

T/C

Type

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

(+) Lead to

Channel High

(-) Lead to

Channel Low

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 DBK84’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. However, the DBK84 inherently provides a high level of noise immunity
via its 4 Hz signal bandwidth and input filtering. If desired, further noise reduction can be achieved

pg. 2, DBK84 989494 DBK Option Cards and Modules

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.

To accommodate shielding, grounded connections, labeled “Analog Common,” are provided. A typical
use of the connection would be to attach the shield of a shielded thermocouple.

If a thermocouple shield is connected to the DBK84 module, leave the shield
unconnected at the other end of the thermocouple.

Open Thermocouple Detection

The DBK84 is equipped with open thermocouple detection for each channel. This means that a broken
thermocouple wire [or otherwise unconnected input] that is measured will result in an off-scale reading.
This is accomplished by applying a small bias current to each of the channel inputs. Whenever a valid
input is absent, the bias current saturates the input amplifier, resulting in the off-scale reading. When in
this
“off-scale” state, however, the input amplifier draws more current from the power supply. Specifically, the
power draw of the module from ±15 V will increase by 0.75 mA for each open channel.

If available power is limited, insert shorted TC plugs into unused channels. This will
minimize power consumption. Note that it is not enough to simply avoid scanning unused
channels; to minimize power consumption the channels must be physically shorted in the
hardware.

The power requirements, detailed in the product specification, assume worst case
connection conditions.

DBK Option Cards and Module 989494 DBK84 pg. 3