Chapter 4. Operation
4.1 Voltage outputs
The Güralp 54T has three single-ended (non-differential) outputs which provide voltages in the range zero to five volts. Four signal ground pins are provided for use with these outputs – they are all electrically equivalent and connected together within the case.
When orientated normally, the outputs will all be at 2.5 V when the unit is subjected to no acceleration other than that due to gravity. A 2.5 V reference output is provided for comparison purposes. Each individual output will be five volts at full scale acceleration (either -1 g or -2 g, depending on the build option) in the corresponding positive direction. The output will be zero volts at full scale acceleration in the negative direction.
Some or all outputs will be offset by a fixed amount if the unit is orientated in any non-standard way. Please see section 4.4 for details.
4.2 Optional current-loop outputs
The standard instrument has single-ended voltage outputs. Instruments can also be ordered with additional current-loop outputs. There are three different current-loop output modes, one of which must be specified at the time of ordering. These modes are:
0-20 mA outputs (10 mA at 0 g)
4-20 mA outputs (12 mA at 0 g)
0-40 mA outputs (20 mA at 0 g)
The outputs are bi-directional current sinks. To use these outputs, apply a DC voltage of between ten and thirty-six volts between the two pins of each output (the polarity is unimportant). The instrument will regulate the current flowing between the pins so that it is proportional to acceleration.
4.3 Switchable output offset
A facility is provided which can apply a switchable voltage offset to each channel. It is controlled by an input pin on the nineteen-way connector. When pin S is connected to a positive DC voltage in the range 5 V to 14 V, the following offsets are added:
Channel | Offset |
East / West | ≈ –210 mV |
North / South | ≈ +210 mV |
Vertical | ≈ –350 mV |
4.4 Orientation
If the instrument is mounted with the axes orientated as indicated on the top cover and the illustration in Appendix C on page 11, full peak-to-peak output is available. If the instrument is mounted in any other orientation, the output is offset as shown in the table below. These examples are all for a ±2 g instrument
Note: An upwards ground movement will result in a decrease in vertical output.
Orientation | 0g Outputs | Range | |
Mounted with all axes aligned N/S and E/W |
| E/W 2.5 V | ±2 g |
Rotated about the N/S axis Connector downwards |
| E/W 1.5 V | -1 g to +3 g |
Rotated about the N/S axis Connector upwards |
| E/W 3.5 V | -3 g to 1 g |
Rotated about the E/W axis Base facing north |
| E/W 2.5 V | ±2 g |
Rotated about the E/W axis Base facing south |
| E/W 2.5 V | ±2 g |
