Guralp Systems Limited
Fortis - Technical Manual

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1. Preliminary Notes 2. Introduction 3. Getting started 4. Installation 5. Accessories 6. Calibration 7. Connector pin-outs 8. Revision History

Section Index: 3.1. Unpacking and packing 3.2. Initial testing 3.3. Setting the gain

Chapter 3. Getting started

3.1 Unpacking and packing

The Fortis is delivered in environmentally-friendly, flat-packable, suspension packaging. The packaging is specifically designed for the Fortis and should be re-used whenever you need to transport the sensor. Please note any damage to the packaging when you receive the equipment and unpack on a clean surface. The package should contain the accelerometer, the calibration pack and either a connection cable, if ordered, or a 19-pin line-socket, to which you can terminate your own cabling.

Caution: Although the Fortis is a strong motion instrument, it contains sensitive mechanical components which can be damaged by mishandling. If you are at all unsure about the handling or installation of the device, you should contact Güralp Systems for assistance.

3.2 Initial testing

Pre-installation testing is most easily accomplished with a Güralp Hand-held Control Unit (HCU) (see section 5.2), which allows access to each individual output and input, but you can quickly assemble a test-rig using a spare connector and a screw-clamp connector block. You will need a DC power supply capable of providing over 100 mA at between 10 and 36 Volts and, if you are not using an HCU, a voltage meter which can measure in ± one-Volt and ± ten-Volt ranges.

If the performance so far has been as expected, the instrument may be assumed to be in working order and you may proceed to install the unit for trial recording tests. In many cases, there will be a slight offset to the readings – this can be disregarded.

3.3 Setting the gain

The gain of the Fortis can be controlled by a rotary switch, recessed into the base of the instrument, or by selectively grounding none, one or both of two control lines, exposed on the main instrument connector.

Pin-out details for the connector are given in Section 7.

Note: The Fortis is delivered from the factory with the gain-setting switch in position 2. This results in a full-scale output corresponding to ±2 g.

3.3.1 To adjust the gain using the switch

Engraved switch position

Amplifier gain

Full-scale (g)

3

1

4

2

2

2

1

4

1

0

8

0.5

Select 0

Select 1

Amplifier gain

Full-scale (g)

Equivalent rotary switch position

low

low

8

0.5

0 (3 engraved)

low

high

4

1

1 (2 engraved)

high

low

2

2

2 (1 engraved)

high

high

1

4

3 (0 engraved)

Pin-out details are given in Section 7.

3.3.2 Gain interaction

Güralp do not recommend attempting to use both gain control methods simultaneously. The following information is provided for completeness only.

The gain control switch acts directly on the two gain control lines, “Select 0” and “Select 1”, grounding neither, one or both as appropriate. The following table shows the effect of using both the switch and the control lines at the same time.

Rotary Switch

Select 0

Select 1

Gain

Full-scale (g)

0

high

high

1

4

high

low

2

2

low

high

4

1

low

low

8

0.5

1

high

ignored

2

2

low

8

0.5

2

ignored

high

4

1

low

8

0.5

3

ignored

ignored

8

0.5

PreviousNext

1. Preliminary Notes 2. Introduction 3. Getting started 4. Installation 5. Accessories 6. Calibration 7. Connector pin-outs 8. Revision History