Tektronix Keithley 3721 Instructions Manual

Dual 1x20 multiplexer card

Hide thumbs

page of 26

/ 26
Bookmarks

Quick Links

Download this manual

Keithley Instruments

28775 Aurora Road

Cleveland, Ohio 44139

1-800-833-9200

tek.com/keithley

Introduction

The Model 3721 offers two independent banks of 1×20 two-pole multiplexers that are ideal for general-purpose

switching, including temperature measurements. The two banks can be automatically connected to the Series

3700A mainframe backplane and optional digital multimeter (DMM) through the analog backplane connection

relays. This connection allows the mainframe to reconfigure the 3721 as a single 1×40 two-pole multiplexer or to

enable card-to-card expansion for even larger configurations.

In addition to the 40 channels, two fused channels are supplied for current measurements. The 3721 includes

dedicated inputs that enable 40 channels of four-wire commonside ohms measurements. For thermocouple-type

measurements, automatic cold junction compensation (CJC) is supported when used with the detachable Model

3721-ST accessory.

The 3721 uses two 50-pin D-sub plugs for signal connections. For screw-terminal connections or automatic CJC,

use the detachable 3721-ST accessory. For more information regarding available cards and accessories, refer to

the Series 3700A System Switch/Multimeter and Plug-in Cards datasheet, available at tek.com/keithley.

Item shipped may vary from model pictured here.

This document describes how to install the plug-in card and make connections to it. For information on scanning,

and on reading, writing, and controlling channels, refer to the Series 3700A System Switch/Multimeter Reference

Manual, available at tek.com/keithley.

077183400 October 2024

Model 3721 Dual 1×20 Multiplexer Card

Figure 1: Model 3721 Dual 1×20 Multiplexer Card

*P077183400*

Instructions

Need help?

Do you have a question about the Keithley 3721 and is the answer not in the manual?

Questions and answers

Summary of Contents for Tektronix Keithley 3721

Page 1 Model 3721 Dual 1×20 Multiplexer Card Keithley Instruments Instructions 28775 Aurora Road Cleveland, Ohio 44139 1-800-833-9200 tek.com/keithley Introduction The Model 3721 offers two independent banks of 1×20 two-pole multiplexers that are ideal for general-purpose switching, including temperature measurements. The two banks can be automatically connected to the Series 3700A mainframe backplane and optional digital multimeter (DMM) through the analog backplane connection relays.
Page 2 Model 3721 Dual 1×20 Multiplexer Card Instructions Safety precautions for connections Shock hazard. To prevent electric shock that could result in serious injury or death, comply with these safety precautions. Connection information for plug-in cards is intended for qualified service personnel. Do not attempt to connect devices under test (DUTs) or external circuitry to a plug-in card unless you are qualified.
Page 3 Model 3721 Dual 1×20 Multiplexer Card Instructions To install a switching card into the instrument mainframe: 1. Turn the instrument off. 2. Position the instrument so that you are facing the rear panel. 3. Disconnect the power line cord and any other cables connected to the rear panel. 4.
Page 4 Model 3721 Dual 1×20 Multiplexer Card Instructions Verify card installation To verify that the card was properly installed: 1. If the 3700A is controlled remotely (REM is displayed), press EXIT to switch control to local. 2. On the 3700A front panel, press SLOT. The name and firmware version of the instrument is displayed. 3.
Page 5 Model 3721 Dual 1×20 Multiplexer Card Instructions You can query the slot attributes to determine the capabilities of the installed switching modules. For example, send the following query to determine if slot 1 supports 4-wire commonside ohms channels: print(slot[1].commonsideohms) Refer to the Series 3700A System Switch/Multimeter Reference Manual for more information about using queries at tek.com/keithley.
Page 6 Model 3721 Dual 1×20 Multiplexer Card Instructions Figure 4: 3721 schematic multiplexer bank 2 in 2-pole mode 077183400 October 2024...
Page 7 Model 3721 Dual 1×20 Multiplexer Card Instructions The following figure shows a switching schematic for the Model 3721 in 4-wire commonside ohms mode. Figure 5: 3721 schematic for four-wire commonside ohms mode Retrieving data from additional backplane relays The Model 3721 card has three backplane relays for commonside ohms functionality. Use slotX or allslots to query settings on this card to return information for channels 1 through 40, 911 through 917, and 921 through 928.
Page 8 Model 3721 Dual 1×20 Multiplexer Card Instructions Screw-terminal accessory The 3721-ST screw-terminal accessory is shown in the following figure. Figure 6: 3721-ST Screw-Terminal Accessory 077183400 October 2024...
Page 9 Model 3721 Dual 1×20 Multiplexer Card Instructions Wire the screw-terminal accessory These instructions describe how to connect wiring to a Series 3700A screw-terminal accessory. It is not necessary to remove a circuit board from its enclosure to wire the screw-terminal accessory.
Page 10 Model 3721 Dual 1×20 Multiplexer Card Instructions 4. As shown in the following figure, route your wiring through the slots at the rear of the screw-terminal accessory and connect it to the wiring terminals as described in Connection information (on page 13). Figure 8: Routing and securing cables with ties 5.
Page 11 Model 3721 Dual 1×20 Multiplexer Card Instructions 7. Slide the cover forward (1) and beneath the retaining tab (2), as shown in the following figure. 8. Fasten the two slotted captive screws (3). Figure 9: Install the screw-terminal assembly top cover Install the screw-terminal accessory Before using a screw-terminal assembly with an installed plug-in card, verify that the card is properly installed in the 3700A instrument and that the mounting screws are tightly fastened.
Page 12 Model 3721 Dual 1×20 Multiplexer Card Instructions 2. Make sure that the mounting screws (1 in the following figure) on the installed plug-in card are secure. Figure 10: Check 3700A card mounting screws 3. Align the screw-terminal assembly D-sub connectors with the connectors on the installed plug-in card, as shown in the following figure.
Page 13 Model 3721 Dual 1×20 Multiplexer Card Instructions Remove the screw-terminal accessory To remove a screw-terminal accessory from an installed plug-in card: 1. Remove all power from the 3700A instrument. 2. Turn the knob on the screw-terminal accessory counter-clockwise until it is completely disengaged. You may need to use a slotted screwdriver to loosen the knob.
Page 14 Model 3721 Dual 1×20 Multiplexer Card Instructions Model 3721-ST screw-terminal accessory channel list The following table shows the relationships between the 3721-ST terminals and the 3721 channels. 3721-ST accessory label 3721 channel MUX 1 OUT Multiplexer # 1 Output 1 through 20 1 through 20 MUX 2 OUT Multiplexer # 2 Output...
Page 15 Model 3721 Dual 1×20 Multiplexer Card Instructions Pin number identification Pin numbers for the Model 3721-MTC-3 D-sub cables are shown in the following figure and table. Connect the drain wire to the shield at both ends of the 3721-MTC-3 cable. Figure 14: Model 3721-MTC-3 connectors Model 3721-MTC-3 pin number identification CONN 1...
Page 16 Model 3721 Dual 1×20 Multiplexer Card Instructions Hardware interlocks This plug-in card can switch high-voltage signals. To prevent exposure to hazardous voltages, the plug-in card includes a hardware interlock. The hardware interlocks are present on the plug-in card and are designed to keep the plug-in card disconnected from the 3700A backplane.
Page 17 Model 3721 Dual 1×20 Multiplexer Card Instructions Engage hardware interlocks To engage the hardware interlocks, you must provide a low-resistance path between the two applicable interlock pins, as shown in the figure in Hardware interlocks (on page 16). This path routes a 5 V power source to an onboard interlock relay, which in turn enables power to the backplane relays.
Page 18 Model 3721 Dual 1×20 Multiplexer Card Instructions Channels 41 and 42 of the 3721 switch card are protected by series fuses on the printed circuit board of the 3721. In the event of an overload, both channels and the DMM input are protected. The two fuses are replaceable. The fuse is rated at 250 V, 3 A fast blow 5×20 mm.
Page 19 Model 3721 Dual 1×20 Multiplexer Card Instructions Figure 17: 3721 fuse locations 10. Replace the fuses as needed. Use only fuses the match the ratings listed above. 11. Slide the top cover toward the D-sub connectors, engaging the cover onto the printed circuit board. 12.
Page 20 Model 3721 Dual 1×20 Multiplexer Card Instructions Power budgeting and calculation Individual relay power consumption generally depends on the type of relay. Latching relays consume power briefly to open or close and are not a concern when budgeting power. Nonlatching relays continuously consume power to maintain their state, so they must be considered when budgeting for power consumption.
Page 21 Model 3721 Dual 1×20 Multiplexer Card Instructions Power budgeting example for six 3721 cards This example is for a fully loaded 3706A-S that has 3721 switch cards in all slots. Slot Card Channel relays closed Backplane relays closed 3721 3721 3721 3721 3721...
Page 22 Model 3721 Dual 1×20 Multiplexer Card Instructions Power budgeting example with multiple cards This example is for a fully loaded 3706A-S with a mix of switch cards. Slot Card Channel relays closed Backplane relays closed 3720 3721 3722 3723 25 (2-pole) 3730 3740 2 (high current)
Page 23 Model 3721 Dual 1×20 Multiplexer Card Instructions Model 3721 connection log Use this table to record your 3721 connection information. Channel Color Description OUTPUT 1 CH10 CH11 CH12 CH13 CH14 CH15 CH16 CH17 CH18 CH19 CH20 OUTPUT 2 077183400 October 2024...
Page 24 Model 3721 Dual 1×20 Multiplexer Card Instructions Channel Color Description CH21 CH22 CH23 CH24 CH25 CH26 CH27 CH28 CH29 CH30 CH31 CH32 CH33 CH34 CH35 CH36 CH37 CH38 CH39 CH40 AMPS41 AMPS42 077183400 October 2024...
Page 25 Safety precautions The following safety precautions should be observed before using this product and any associated instrumentation. Although some instruments and accessories would normally be used with nonhazardous voltages, there are situations where hazardous conditions may be present. This product is intended for use by personnel who recognize shock hazards and are familiar with the safety precautions required to avoid possible injury.
Page 26 For safety, instruments and accessories must be used in accordance with the operating instructions. If the instruments or accessories are used in a manner not specified in the operating instructions, the protection provided by the equipment may be impaired. Do not exceed the maximum signal levels of the instruments and accessories. Maximum signal levels are defined in the specifications and operating information and shown on the instrument panels, test fixture panels, and switching cards.

This manual is also suitable for:

Keithley 3721 st Keithley 3721 mtc 15