GRAS 12AU 1-Channel Universal Power Module With Signal Conditioning And Power Amplifier Instruction Manual

Overload Response in Latch Mode
For each of the overload detectors, an internal overload status flag is reflecting the actual overload condition. The overload status flag will be set when an overload occurs.
In latch mode, the status flag and the LED will be set by an occurrence of overload. It can only be reset after the overload condition has been removed and the overload status is read by sending the OVL command (SOVL, COVL or MOVL respectively).
Note: The command: OVLLED N will disable the conditioning amplifier’s overload LED, the behavior in all other ways is unchanged.
Note: the Monitor rear output has no overload LED indication, it can only be read via the USB interface.
Overload Response in Message Mode
When an overload detector is in message mode, the respective overload LED will follow the overload status flag, unless it is disabled by the command: OVLLED N.
The Overload LED will light under overload condition; it will turn off approximately one second after the condition has been removed. For the conditioning amplifier, the time can be shortened by the command: OLVTM M.
When the overload state changes, the message sent will be:
OVL_on or OVL_off or
SOVL_on or SOVL_off or
COVL_on or COVL_off or
MOVL_on or MOVL_off.
If an overload occurs while a command is sent to the 12AU, the overload status will not be read and no response sent back until the command has been processed.
Restart and Default

disabled during this and 12AU restarts when ready.

Default Settings
The conditioning amplifier powers up in default mode, which can be user defined. The factory defined default mode is:

• Conditioning amplifier gain 0 db
• Conditioning amplifier polarization 200 V
• Conditioning amplifier high pass filter 1Hz
• Displays overload
• Overload hold time 1 sec.
• Overload mode is Message mode
• Speaker amplifier gain –20 dB
• Speaker enabled.
• Speaker amplifier high pass filter 10 Hz
• Current output gain 0 dB
• CCP input disabled
• FastSettling disabled
• Monitor set for Conditioning amplifier

Installing the USB-driver and Control Software

The 12AU is operated remotely via its USB interface. Before connecting the 12AU to your computer, you need to install the USB driver and the control software for the 12AU.
Important: Do not connect the 12AU to the PC before installing the device driver.
If you already have done so, you need to update the driver from the Device Manager with the one found on the USB stick in the directory usb_driver! Refer to “Updating the USB driver” on page 30 for information on how to do this.
Installing the USB Driver
Prior to connecting the 12AU, you must install the dedicated USB device driver on the PC that you will use to operate the 12AU.
Important. The installation requires that you are logged in as administrator on the PC.

1. Insert the 12AU USB stick delivered with the 12AU in your PC.
2. In Windows Pathfinder, open the 12AU Installation USB.
3. Open the usb_driver directory containing the USB driverinstaller.
4. Click on the USBDriverinstaller Icon.
5. Click on the Install Drivers button and wait for confirmation.

If you have already connected the 12AU, the installation will fail and you need to remove the Windows USB driver manually by updating the USB driver using the Windows Device Manager.
For instructions on how to do this, see “Updating the USB driver” on page 30.
Installing the Control Software
Introduction
The control software for the 12AU is installed from the installation USB. Windows XP, Windows Vista, or Windows 7 is required.
Screen resolution must be set to 1024 x 768 or higher.
Important. The installation requires that you are logged in as administrator on the PC.
Requirements

• Operating system: Windows XP, Windows Vista, or Windows 7.
• Screen resolution 1024 x 768 or higher.
• A mouse or other suitable pointing device.
• USB port.

Installation

1. Insert the Control software USB stick for 12AU in your computer.

2. Run setup from the root of the installation disk.

3. Click OK (left) , then click the Installation button (right).

When the installation is complete, the control software will be selectable in the program list as 12AU. Once installed, you can drag and drop a shortcut icon from the Windows program list to your desktop.
If the control software does not appear in your program list, you can find it in the folder in which it has been installed. In the example above, that folder is GRAS.
You can operate the 12AU using its graphical interface and a mouse. How to do this is described in “Using the Graphical User Interface” on page 23. Alternatively, you can enter commands in the View Log window. How to do this is described in “Operating the 12AU Using Commands” on page 28.

Preparing the 12AU for Measurements

Cables and Connections
Important! 12AU must be turned off before connecting or disconnecting the USB cable.
Important! Before connecting the 12AU to your PC, you should install the USB driver. Refer to “Installing the USB Driver” on page 18 for instructions.
A typical set-up for testing the loudspeaker of a telephone is shown in Fig. 3 below.

• The signal for the measurement is generated by a signal generator and fed via a BNC cable to the power amplifier.
• The output of the amplifier is taken out as a voltage signal (2-pin LEMO) or a current signal (BNC) and fed to the test object.
• The microphone in the coupler can be an externally polarized microphone (connected with 7-pin LEMO), or a prepolarized microphone connected with a BNC cable.
• The signal picked up by the microphone is fed to the analyzer via a BNC cable.
• For comparison, these signals can be monitored separately during the measurement.
  Connection is via BNC and the monitoring is software-controlled.

Multi-channel Measurements
The 12AU is designed especially for production line testing.
Multiple 12AUs can be set up for simultaneous monitoring of separate production lines, using the same PC as the common control center.
Physically, all 12AUs are connected as shown in Fig. 3 on page 21, but all connected to the same PC via USB.
You can launch a separate instance of the control software for each 12AU connected to the PC.
The control software will automatically look for a 12AU and lock to its serial number.
Each 12AU can be given a name/assigned an identification, making it easy to separate it from other 12AUs controlled from the same PC. For information about how to do this, see “Save Settings as Default in 12AU” on page 27.
Important. Before connecting the 12AU to your PC, you must install the USB driver. Refer to “Installing the USB Driver” on page 18 for instructions.

Operating the 12AU via its PC Application

This section describes how to operate the 12AU using its graphical user interface. Alternatively,
you can use commands. How to do this is described in “Operating the 12AU Using Commands” on page 28.
Using the Graphical User Interface
To launch the 12AU control software, select it from the Windows program list. Fig. 4. The 12AU in the Windows program list.
When the control software is launched, the user interface shown in Fig. 5 is displayed.The 12AUs graphical user interface resembles the front panel. You can operate the 12AU using the pull down menus and by clicking the LEDs representing the settings of the sections of the 12AU.
Selecting Settings

1. Change a setting by clicking the LED symbol below the setting in question. The LEDs will turn green or get dimmed to confirm your choice.

All the settings shown on the user interface can be chosen in this way. For example, you can select 200 V polarization voltage by clicking on the corresponding LED.
The application will store the settings for each 12AU in the Windows registration data base, and will start as when it was closed.
The Setup Menu
The Setup menu lets you select how Overload and Settling time are handled.

• Latched polling 1s
• Latched polling 5s
• Latched, click LEDs to read and reset
• Messaged
• Messaged, latched, click LED to reset
• Disabled
• 0.5 sec
• 1 sec
• 3 sec

The Tools Menu
In the Tools menu, you can

• Activate the View log window in which you can monitor the communication between the control application and the 12AU. See “View Log” on page 25.
• View amplifier temperature, See “View Temperature” on page 25.
• Enlarge the graphical user interface. See “Enlarge the Graphical User Interface” on page 25.
• Select Enable advanced, allowing you to
  – assign a name to 12 AU, See “Assign a Name” on page 26.
  – save actual settings as default setup in 12AU. See page 27.
  – choose to operate the 12AU using commands. See page 28.
  These functions are described in detail on the following pages.

View Log
Selecting the View log option lets you monitor the communication to and from the 12AU. In Fig. 9 an example of this is shown, The example shows how the default setup used by 12AU upon power up is displayed. View Temperature
In the Tools menu, you can enable monitoring of the amplifier temperature (View amplifier temperature). The actual temperature is shown in the status bar, see Fig. 10. Enlarge the Graphical User Interface
In the Tools menu, you can select to Enlarge the graphical user interface. The result is shown in Fig. 11. Enable Advanced
Selecting the Enable advanced option activates a number of functions that otherwise are hidden and therefore inaccessible.

• You can give the 12AU a name. This is useful if you will be operating more than one 12AU from the same PC.
• You can Save setup as default in 12AU. This is used to store the actual settings in the 12AU.
• You can choose to operate the 12AU in command mode. See “Operating the 12AU Using Commands” on page 28 for further information.

To enable advanced:

1. Select Enable Advanced, The Advanced password pop up window will appear. To access this function, you need to enter the password gRas in the Advanced password pop up window. This password is hard-coded into the firmware and cannot be changed. You must type it exactly as shown here.
2. Type gRas and press Enter. The name field shown in the status bar appears, see Fig. 13

Assign a Name
When you have entered the password, you can give the 12AU a name in the name field shown in the status bar, see Fig. 13.

1. Type a name, press Enter.

The 12AU will disconnect and reestablish the connection to the PC application. After a few seconds, its new name will be shown in the status bar as shown in Fig. 14As long as the Enable advanced function is enabled, the name can be changed (and the other advanced functions are accessible). If you want to disable advanced at this point:
Disable Advanced

1. Click on the Tools menu as shown in Fig. 15
2. Click on Enable advanced to remove the disable Enable advanced option.

To edit the name or access the other Enable advanced functions, you need to proceed as described in “Enable Advanced” on page 26.
Save Settings as Default in 12AU
It is possible to store the actual settings as default setup in the 12AU. This feature makes it possible for the 12AU to start up in a user defined setting independently of the control software and the communications link to the PC.

1. In the Tools menu, select Enable advanced as described on page 26.
2. Enter the password gRas as described on page 26.
3. Select the settings you want by clicking the appropriate LEDs.
4. Select Save setup as default in 12AU.
   Now the 12AU will restart and reconnect to the PC.

The Help Menu
The Help menu shows the actual version of the control software, see Fig. 18

Operating the 12AU Using Commands
This section describes how you can operate the 12AU using commands comprising ASCII characters.
They are entered and responses viewed in the G.R.A.S Type 12AU log window found in the Tools menu as shown in Fig. 19. Entering Command Mode
To operate the 12AU in command mode, you must first Enable advanced in the Tools menu and then enter the password as described on page 26. Proceed as follows:

1. Click on the Tools menu.
2. Select Enable advanced.
3. Type the password in the Advanced password window
4. Select View log to display the Type 12AU Log window
5. In the Tools menu of the GRAS Type 12AU log window, select Command mode.
   The graphical user interface disappears and you can now operate the 12AU using commands.

Typing Commands

1. Type each command and strike the key (symbolized by ). Wait for the response.

A typical command will look like this: HP1. This command will set the high-pass filter to 1 Hz.
For a full list of commands, refer to “List of Commands and Responses” on page 12.
Note: When pressing Enter the line up to the cursor will be sent to 12AU.

Dealing with Overload in a Production Setup

Overload Caused by Handling
In a setup with product testing in an automated production line, overload due to handling between measurements may occur.
Minimizing Overload
You can minimize overload by following these guidelines:

• Keep the gain as low as possible.

• Select a microphone with the highest possible high-pass cut-off frequency. This will give the shortest settling time after handling.

• If possible, use the HP20L filter. This produces a little more noise than the HP20 filter but improves the headroom before filtering and thereby reduces the overload.
  The HP20L filter setting applies most of the gain at the output amplifier, e.g. 30 dB will be achieved with 10 dB at the input and 20 dB at the output. (Normally, the most gain will be applied at the input amplifier to achieve best signal to noise ratio).

• If overload is unavoidable, the overload indication hold time can be reduced to a minimum with the command: OVLTM M.

• If you are certain that the overload does not harm your measurement, you can disable the displaying of the overload on the front panel with the command: OVLLED N.
  This will not change the behavior of overload handling on the USB interface.

Appendix

Updating the USB driver
The 12AU uses a dedicated USB driver, it will not work with Windows’ own default USB driver.
If you connect the 12AU to tour PC before installing the USB driver, the installation software cannot install the driver.
To circumvent this problem, you need to update the driver using the Windows Device Manager from the Windows Control Panel.

1. Open the Control Panel in the Windows Start menu
2. Select Hardware and Sound.
3. Select Device Manager. The 12AU will be listed under Other Devices.
4. Right-click CDC RS-232 Emulation GRAS and select Properties.
5. Select the tab General and click the Update Driver button.
6. Click Browse my computer for driver software to access the 12AU installation USB.
7. Select usb_driver on the Installation USB.
8. Ignore the authenticity warning. The USB driver will now be updated with the Microtech USB driver required by the 12AU.

Technical Specifications

All outputs except speaker amp. output have fixed 100 kHz (3 dB) low pass filters to minimize the need for anti-aliasing filtering in the following analyzing equipment.
There is no phase shift between microphone input and output due to prepolarized or external polarized microphones. It is designed with no relays in the signal path.
Microphone section

Noise floor (relative to input)
Input shorted (≥20 de gain)
Input loaded with 20 pF dummy mic.| <1.5 pVrms (20 Hz – 20 kHz)
<5 pVrms (20 Hz – 20 kHz)
High pass filter (remote controlled) 1.order
Butterworth 3. order| 1 Hz 20 Hz
Overload detection| LED indicators (remote controlled)

Speaker-amplifier section

power ground)
Gain (remote controlled)| -20 db to +10 dB in 10 dB steps (±10.2 dB)
Bandwidth (-3d13)
(remote controlled AC or DC coupling)| DC coupled: DC to 80 kHz
AC coupled: 10 Hz – 80 kHz
Phase shift (input to output)| ≤ ±1° (DC to 20 kHz)
Max output voltage| ±13.5 V
Max output current| ±1.4 A
Voltage and current overload detection| LED indicator (remote controlled reading and reset)
---|---
Current output (voltage/current ratio)| 1 V /1 A or 10 V/1 A

Monitor Output Section

The monitor socket on the front is for quick check – its performance is (slightly) below that of the similar socket on the rear.
Power
Power Supply| 115 or 230 VAC

Warranty and Service

Warranty
All GRAS products are made of high-quality materials that will ensure life- long stability and robustness. The 12AU is delivered with a two-year warranty.
The warranty does not cover products that are damaged due to negligent use, an incorrect power supply, or an incorrect connection to the equipment.
Service and Repairs
All repairs are made at GRAS International Support Center located in Denmark. Our Support Center is equipped with the newest test equipment and staffed with dedicated and highly skilled engineers. Upon request, we make cost estimates based on fixed repair categories. If a product covered by warranty is sent for service, it is repaired free of charge, unless the damage is the result of negligent use or other violations of the warranty. All repairs are delivered with a service report, as well as an updated calibration chart.

Manufactured to conform with:
CE marking directive: 93/68/EEC
WEEE directive:
2002/96/EC
RoHS directive:
2002/95/EC G.R.A.S. Sound & Vibration continually strives to improve the quality of our products for our customers; therefore, the
specifications and accessories are subject to change.
LI0083 – Revision 28 October 2021

References

• GRAS Sound and Vibration

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