Mux80 AIN Expansion Board

Summary

The Mux80 AIN Expansion Board serves to provide an additional 80 analog inputs to any compatible LabJack.  It uses 10 multiplexer chips connected to AIN4-AIN13, and splits each channel into 8 additional channels.  When a specific extended analog input channel is read on a U6, UE9 or T7, the digital output MIO lines are automatically set, and the correct analog channel is read.  The Mux80 has a built-in DC-DC converter which provides the upper and lower rail voltages necessary for powering the multiplexer chips.

Three vertical DB37 connectors provide an easy interface to connect 24 AIN channels each. The remaining connector brings out unused connections (FIO, DAC, etc) from the LabJack, along with the last 8 AIN channels. There are a total of 84 available analog inputs when used in conjunction with a U6, UE9 or T7.

• 80 Multiplexed Channels (or 40 Differential Pairs)
• Built-In DC-DC Converter
• OEM Capability
• Easy-To-Use High Density Connectors
• Snaptrack/DIN-rail compatible, with TE Connectivity P/N TKAD

Connection Options

The Mux80 can be connected several ways.  The images below demonstrate use with the CB37 Terminal Board, and several 3ft DB37 Cables.

When connected to a CB37, there is a quick way to determine which screw terminals can be used as analog inputs; reference the chart printed on the top of the Mux80, also shown below for reference.

For example: A signal is connected to FIO6 on a CB37.  The CB37 is connected to X4 on the Mux80, so on the chart, under X4 and FIO0-7, locate MUX88-95.  So the signal is connected to MUX94.  To read MUX94 simply perform a standard AIN read for analog input number 94.

Connector X2 is essentially a duplicate of the DB37 connector on the main device, except AIN4-11 are instead Mux120-127, and AIN12-13 are not connected to anything. On connector X2, AIN0-3 are duplicates of the main device, as well as FIO, DAC, etc.

Using Differential Analog Inputs with the MUX80: The normal rule for differential inputs is that the positive channel must be even and the negative channel must be positive+1, but this is only true for AIN0-AIN13. Since AIN4-AIN13 are not available when using the Mux80, this normal rule only applies to AIN0-AIN3, and for those the positive channel will be either AIN0 or AIN2 and the negative channel will be AIN1 or AIN3, respectively. When using extended channels, the positive channel can be any channel (even or odd) listed under the “P Channel” heading in the chart below. The negative channel is P Channel+8 (listed under the “N Channel” heading in the chart below).

Example 1: The positive channel is connected to M102 (AIN6 on the CB37 connected to X5). The corresponding negative channel is M110 (DAC0 on the CB37 connected to X5).

Example 2: The positive channel is connected to M64 (FIO0 on the CB37 connected to X3). The corresponding negative channel is M72 (AIN0 on the CB37 connected to X4).

The following chart summarizes the positive and negative channel numbers for differential analog inputs with the Mux80.  Note that for some differential pairs, the positive and negative are located on different connectors.

When using the Mux80 with a Modbus compatible device, such as the T7, use the following registers to read the extended analog inputs.

For more information on multiplexing with the U6, see U6 Channel Numbers 

For more information on multiplexing with the UE9, see UE9 Channel Numbers

Pin-out

J1-J5 are OEM pin-header locations, and appear immediately next to the DB37 connectors.  A 40 pin (2x20) 0.1" spacing header fits the location.

X1 is the Male DB37 connector which interfaces with the LabJack.

X2-X5 provide access to the 80 Mux channels, along with the FIO, DAC, VM+, VM-, and MIO lines.  Please reference the spreadsheet below for exact pin locations.

Specifications

Using Extension Cables

When using extension cables, the effect of ground currents should be considered, especially when substantial current is being sourced/sunk though the CB37 and Mux80 grouping.  In an effort to reduce the impact of ground currents, AGND is supplied on the Mux80 in the same pin configuration as on the LabJack.  So AGND on the CB37 (while connected to a Mux80) is the same as it would be if it was connected directly to the LabJack.  

See the CB37 Datasheet for more information on AGND, and common techniques for handling offsets created by ground currents.

Dimensions

Below is an image describing the locations of the mounting holes, OEM connectors, and total board size.  Based on the origin in the bottom left corner, each coordinate is shown in parenthesis (x, y).  OEM connector coordinates (J1-J5), indicate the location of pin 1; the remaining pins follow knowing that the header is a standard 0.1" spacing.

Troubleshooting

It is possible to check Mux80 functionality in LJControlPanel by performing the following steps:

1. Open LJControlPanel
2. Select UD device and click Test
3. On test pane, locate MIO 00, MIO 01, MIO 02 checkboxes for both Digital Direction and Digital State
4. Check the boxes for all 3 MIO lines under Digital Direction
5. Check desired boxes under Digital State according to the following table.  Simply find the extended channel number to investigate, then trace across the row to the Output State of MIO0, MIO1, and MIO2.  Set the output state to high (checked) for 1 and low (un-checked) for 0.
6. Trace the column up to AIN#, this is the analog input that your analog signal will appear on. 

For example:  I have connected an analog signal to Mux65.  If I am using a CB37 Terminal Board, this will mean that the CB37 is connected to X3 on the Mux80, and the signal is wired to FIO1 on the CB37.  Looking at the above chart I note that 65 shares a row with MIO Output States of 1,0,0.  I then set MIO0 checked, MIO1 unchecked, and MIO2 unchecked.  Next I follow the column for 65 up to AIN6, so that is the analog input where I will see my analog signal with this MIO configuration.

If there seem to be problems with incorrect readings, also check that VMUX+ and VMUX- are within specified limits by measuring the test points with respect to GND. 

Notes: 

• Insure your device has the latest firmware.  There is a known U6 firmware issue concerning MIO lines in v1.26 and older.  See revision history for more info. U6 firmware v1.40 and newer is able to stream differential channel pairs with the Mux80.
• On the U6, and U6-Pro device the digital lines CIO0-2 and MIO0-2 are shared.  This means that changing the state of MIO0-2 will also change the state of CIO0-2.  Therefore, anyone using a Mux80 with a U6 needs to be aware that digital lines CIO0-2 are not usable.