Vibrating Wire Sensor Installation
The vibrating wire sensors are connected directly into the Sensor Input channels on the VibWire-108 and supports full 4 wire gauge sensors. The instrument contains a completion resistor for the thermistor sensor enabling the temperature reading to be made along with the vibrating wire sensor readings.
Connection to the instrument is as follows:
The vibrating wire sensors are connected directly into the Sensor Input channels on the VibWire-
Connection to the instrument is as follows:
+
Sense
-
Sense
-
+
Therm
-
Therm
-
+
Sense
-
Sense
-
+
Therm
-
Therm
-
Common Earth/Gnd Points
In order to ensure that there are sufficient points to terminate sensor sheathing when amoured cable is used to connect a sensor to the VibWire-108 the following terminal points are internally wired in common:
Earth
Earth
Earth
Earth
Gnd
On the power supply connection terminals
Therm -
Sense -
on both the sensor input and analogue output terminals.
Fig 14 shows how the channels are wired together to form common earth connection. Effectively all of the Earth, Gnd, Sense - and T herm - terminals are wired together.
Any earth Sheathing from armoured cable etc.. can be connected to any of terminals mentioned above for ease of installation.
Lightening Protection
The lightening protection within the VibWire-108 cannot protect the instrument from a direct lightening strike. It is used to protect the instrument from local ground strikes close to the sensors and cabling.
All of the sensor inputs are protected by transorb and gas discharge tubes. The transorb are high capacitance devices and are not used on all systems as they can distort low level signals to a point where the instrument can not be accurately measured. The transorb does protect the instrument at lower levels than the gas discharge tube, and starts to become active around 12V.
The gas discharge tube protection activates at around 92V DC and resets instantaneously after
Fig 14 shows the VibWire-108 connected to a system earth using the Earth terminators mounted adjacent to the power connectors.
+
Sense
-
Sense
-
+
Therm
-
Therm
-
VW-108
Thermistor
Multiple Instrument Installation
Figure 16 shows how to Earth multiple instruments within a single enclosure. Ensure that good quality cable of around 2.5 mm diameter core is used to connect the instruments earths together and that a good connection to a main system earth is obtained. The Earth connection is essential for the lightening protection to work.
PCB Jumper Settings
All of the VibWire-108 models support thermistor, analogue input for the range 0 - 2.5 V DC and current loop inputs.
For current loop operations such as those 0- 20 mA, 4- 20 mA then external excitation is required.
Jumper Open = 0-2.5V DC
4-20 mA loop
Jumper Closed = Thermistor
For current loop operations such as those 0-
Jumper Open = 0-
4-
Jumper Closed = Thermistor
PCB Jumpers
Figure 14
Earth
Earth
Earth
Earth
Figure 13
Figure 12
Figure 11