background image

INSTALLATION GUIDE

TBX-68S Isothermal Terminal Block

This installation guide describes how to install and connect signals to the 
TBX-68S isothermal terminal block for use with the NI 2501 and NI 2503 
PXI switch cards.

Contents

Introduction ............................................................................................. 1
What You Need to Get Started ............................................................... 2
Signal Connection ................................................................................... 2
Installing Your Terminal Block .............................................................. 3
Rack-Mounting the TBX-68S ................................................................. 5
Cold-Junction Temperature Sensor......................................................... 5
Specifications .......................................................................................... 7

Introduction

The TBX-68S is an isothermal DIN-rail mountable terminal block that 
consists of a shielded board with screw terminals that connect directly to 
the front panel I/O connector of the NI 2501 or NI 2503.

The terminals blocks can easily accommodate thermocouples, resistance 
temperature detectors (RTDs), thermistors, and voltage signals. The 
terminal blocks feature isothermal construction to minimize the 
temperature gradients across the screw terminals and a high-accuracy 
thermistor cold-junction temperature sensor for measuring with 
thermocouples. Enclosures keep out air currents to maintain an isothermal 
environment for the screw terminals and the cold-junction sensor. The 
TBX-68S mounts on most European standard DIN EN mounting rails.

The TBX-68S provides screw terminal connections to all channels except 
the cold-junction sensor.

̭͈Ρ΅νιϋΠ͉ͅȂ඾ུࢊβȜΐ͜܄̞̳ͦ̀͘͘ȃ

Summary of Contents for TBX-68S

Page 1: ...nals that connect directly to the front panel I O connector of the NI 2501 or NI 2503 The terminals blocks can easily accommodate thermocouples resistance temperature detectors RTDs thermistors and voltage signals The terminal blocks feature isothermal construction to minimize the temperature gradients across the screw terminals and a high accuracy thermistor cold junction temperature sensor for m...

Page 2: ...t your signals Refer to Figure 1 as you perform the following steps to connect your signals to your terminal block 1 Remove the terminal block cover by unscrewing the four cover screws in the cover corners using the Phillips head screwdriver 2 Use wire cutters and wire insulation strippers to strip the wire ends as necessary to connect them to screw terminals 3 Loosen the screws in the screw termi...

Page 3: ...temperature differentials Refer to Figure 2 as you perform the following steps to connect the terminal block to the NI 2501 or NI 2503 connector 1 Attach the connector on one end of the cable to the NI 2501 or NI 2503 connector The two connectors should snap together in place 2 Attach the connector on the other end of the cable to the terminal block connector If you use the SH6868S cable the two c...

Page 4: ...Caution The connectors of both the switch card and the cable are polarized You can attach them in only one way Do not force the cable when inserting it into or removing it from the NI 2501 or NI 2503 connector Figure 2 Connecting the TBX 68S Cable Assembly 1 NI 2501 or NI 2503 2 SH6868S Shielded Cable shown or R6868 Ribbon Cable 3 Signal Wires 4 TBX 68S 5 Ejector Ears 1 2 4 3 5 ...

Page 5: ...sor voltage output varies from 198 54 mV to 19 58 mV over the temperature range 0 to 55 C respectively and has an accuracy of 0 5 C over the 15 to 35 C temperature range and 0 9 C over the 0 to 15 and 35 to 55 C temperature ranges 1 You can use the following formulas to convert the cold junction sensor voltage to cold junction temperature T C TK 273 15 where TK is the temperature in kelvin a 1 295...

Page 6: ... channel of your measurement device The 200 mV range is designed to eliminate the necessity of changing a measurement device s signal range to measure the cold junction sensor while scanning thermocouples Use an average of a large number of samples to obtain the most accurate reading Noisy environments require more samples for greater accuracy Figure 3 shows the circuit diagram of the TBX 68S cold...

Page 7: ...sions 12 7 by 11 2 by 7 62 cm 5 0 by 4 4 by 3 0 in Max voltage signal common mode Each input should remain within 30 Vrms or 60 VDC of ground and all other channels to eliminate the possibility of hazardous shock 1 Includes the combined effects of the temperature sensor accuracy and the temperature difference between the temperature sensor and any screw terminal The temperature sensor accuracy inc...

Page 8: ...nal Instruments trademarks Other product and company names mentioned herein are trademarks or trade names of their respective companies For patents covering National Instruments products refer to the appropriate location Help Patents in your software the patents txt file on your CD or ni com patents 1998 2007 National Instruments Corporation All rights reserved 372262B Nov07 ...

Reviews: