Shim Amplifier

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Shim Amplifier front

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Shim Amplifier rear

This module allows you to drive up to 8 shim coils with current controlled output of up to 1 Amp.

Features:

  • 8 channel shim amplifier

  • Dual Heater Driver

Connections

On front of the Shim Amplifier module you will find the on/off power switch and the indicator lights. The top indicator will illuminate green when the module is powered on, while the bottom indicator will illuminate blue when the amplifier is enabled via the interlock.

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Front controls & indicators

The 24 V power port, Shim in/out connectors, I/O port and temperature control connectors can be found on the back of the module.

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Rear ports

Setup Guide

This section will guide you through the steps required to connect and power the Shim Amplifier Module with the Kāhu Spectrometer.

Warning

Ensure the Shim Amplifier module is not powered on during Kāhu power up and shutdown.

Step 1 - Rear Cable Connections

Begin by arranging the modules as shown in the image below with the Kāhu Spectrometer placed on top of the drive module(s). Note that the image below also shows the Gradient module in the stack-up. This module is not required to run the shim amplifier, and if it is not being used simply place the Shim amplifier module to the side of Kāhu.

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Kāhu, Shim & Gradient Amplifier modules stacked

Complete the initial rear Kāhu connections as explained in the Kāhu Hardware Connections section. Connect the 24V, 120 W external power brick to the shim amplifier.

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Power supply: 24V, 120W

Fasten the 10 pin I/O connector to the Shim Amplifier’s I/O port using the provided drive tool, H2.0. Take care to not overtighten.

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IO cable connection, shim amplifier side

Connect the other end of the I/O cable to Kāhu’s interlock and PT100 ports as shown.

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IO cable connection, Kāhu side

Connect the provided Shim control cable between the Shim In port on the Shim Amplifier Module and the Shim port on Kāhu. Should you need to replace this cable, the part number is Samtec FCF8-20-01-L-12.00-S.

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Shim control cable connection

Note

The shim control cable is oriented with the gold contacts facing upwards when connecting to Kāhu, but facing downwards when connecting to the amplifier module.

Finally, connect the shim out port to your shim coils. You will need to build our own cable for this connection. The mating connector required for the cable is the Harwin M80-4141698 and the arrangement of the shim channels from the amplifier is shown below.

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Shim output connector, Shim Channels

Step 2 - Power Up

Power on Kāhu and establish a network connection from your PC. Once Kāhu power up has finished, you can power on the Shim Amplifier with the power switch.

Specifications

General

Power Supply

24 V, 120 W

Dimensions

150 x 200 x 65 mm (Width x Depth x Height)

Weight

1 kg

Heater Driver

Channels

2

Output Voltage

24 V

Max total output current

2 A [1]

Mating Connector

Adam Tech MMI-M0PG05S52

Shim Drivers

Channels

8

Input Range

±5 V, single ended

Transconductance Gain

0.2 A/V

Output Voltage Range

±5 V

Output Current Range

±1 A

Shim Coil Resistance

3 - 5 Ω

Detailed Description

Amplifier

Each shim amplifier channel consists of a single stage voltage controlled current source. The output current will be proportional to the input voltage according to the following transfer function:

\[I_{out} = 0.2 * V_{in}\]

I/O Port

The part number for the mating connector used in the I/O cable privided (on the amplifier side) is the M80-4141298. The pinout of the I/O port on the module is:

Pin No.

Description

1

PT100 1+ output

2

PT100 1- output

3

PT100 1 reference output

4

PWM 1 input

5

PWM 2 input

6

Interlock input

7

PT100 2+ output

8

PT100 2- output

9

PT100 2 reference output

10, 11, 12

GND
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Shim IO connector pinout

Note

Do not connect a PT100 sensor to this port, instead use the T-1 or T-2 port(s) as described in the Temperature Control section below.

Temperature Control

Two independent heaters can be driven by the module via the T1 and T2 ports. Using the Temperature Control tab of the System dashboard, the duty cycle of the heater driver can be automated to achieve a temperature set point.

The mating connector required to build the temperature control cable is the Adam Tech MMI-M0PG05S52.

The pinout of both temperature control ports on the module is as follows:

Pin No.

Description

1

Heater +

2

Heater -

3

PT100 Reference

4

PT100 -

5

PT100 +
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Temperature control ports pinout

Caution

To avoid damage, take care to align the red orientation markers on the connector and port

Maintenance

To ensure the module doesn’t begin to overheat, the dust filters should be cleaned regularly. To access the filters, ensure the module is powered off then remove the 4 screws on the panel on the under side of the module as seen below. The filters can then be removed, cleaned, and refitted.

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Dust filter cover removed

Note

Ensure filters and panels are refitted before the module is powered back on.