Showing posts with label wire. Show all posts
Showing posts with label wire. Show all posts
Friday, September 19, 2014
Two Wire Temperature Sensor
Remote temperature measurements have to be linked by some sort of cable to the relevant test instrument. Normally, this is a three-core cable: one core for the signal and the other two for the supply lines. If the link is required to be a two-core cable, one of the supply lines and the signal line have to be combined. This is possible with, for instance, temperature sensors LM334 and LM335. However, these devices provide an output that is directly proportional to absolute temperature and this is not always a practical proposition.
Circuit diagram :
Two-Wire Temperature Sensor Circuit Diagram
If an output signal that is directly proportional to the celsius temperature scale is desired, the present circuit, which uses a Type LM45 sensor, offers a good solution. The LM45 sensor is powered by an alternating voltage, while its out-put is a direct voltage.
The supply to the sensor is provided by a sine-wave generator, based on A 1 and A 2 (see diagram). The alternating volt-age is applied to the signal line in the two-core cable via coupling capacitor C 6 .
The sensor contains a volt-age-doubling rectifier formed by D 1 -D 2 -C 1 -C 2 . This network converts the applied alternating voltage into a direct voltage. Resistor R 2 isolates the output from the load capacitance, while choke L 1 couples the output signal of the sensor to the signal line in the cable. Choke L 1 and capacitor C 2 protect the output against the alternating voltage present on the line.
At the other end of the link, network R 3 -L 2 -C 4 forms a low-pass section that prevents the alternating supply voltage from combining with the sensor out-put. Capacitor C 5 prevents a direct current through R 3 , since this would attenuate the temper-ature-dependent voltage.
The output load should have a high resistance, some 100 kΩ or even higher. The circuit draws a current of a few mA.
Monday, September 8, 2014
Two Wire Temperature Sensor
Remote temperature measurements have to be linked by some sort of cable to the relevant test instrument. Normally, this is a three-core cable: one core for the signal and the other two for the supply lines. If the link is required to be a two-core cable, one of the supply lines and the signal line have to be combined. This is possible with, for instance, temperature sensors LM334 and LM335. However, these devices provide an output that is directly proportional to absolute temperature and this is not always a practical proposition. Circuit diagram : ![]()
Two-Wire Temperature Sensor Circuit Diagram If an output signal that is directly proportional to the celsius temperature scale is desired, the present schema, which uses a Type LM45 sensor, offers a good solution. The LM45 sensor is powered by an alternating voltage, while its out-put is a direct voltage. The supply to the sensor is provided by a sine-wave generator, based on A 1 and A 2 (see diagram). The alternating volt-age is applied to the signal line in the two-core cable via coupling capacitor C 6 . The sensor contains a volt-age-doubling rectifier formed by D 1 -D 2 -C 1 -C 2 . This network converts the applied alternating voltage into a direct voltage. Resistor R 2 isolates the output from the load capacitance, while choke L 1 couples the output signal of the sensor to the signal line in the cable. Choke L 1 and capacitor C 2 protect the output against the alternating voltage present on the line. At the other end of the link, network R 3 -L 2 -C 4 forms a low-pass section that prevents the alternating supply voltage from combining with the sensor out-put. Capacitor C 5 prevents a direct current through R 3 , since this would attenuate the temper-ature-dependent voltage.
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The output load should have a high resistance, some 100 kΩ or even higher. The schema draws a current of a few mA.
Tuesday, August 12, 2014
EXCITATION WINDING AND AVR SENSING WIRE CHECKING Wacker Neuson GP 2600 GP 4000 Generator
How to check Excitation Winding _ AVR’s Sensing Wires _ Wacker Neuson GP 2600 - GP 4000 - GP 5600A / GPS 5600A - GP 6600A / GPS 6600A Generators
Checking Excitation Winding
The excitation winding provides AC voltage to the Automatic Voltage Regulator (AVR). The AVR then sends a DC voltage through the rotor winding “exciting” the rotor into becoming an electromagnet. To check the excitation winding, carry out the following procedures:
* Stop the engine.
* Remove the two screws which secure the end cover to the generator and remove the end cover.
* Remove the plug (a) which connects the excitation winding to with the AVR. On GP 2500A/GP 2600 models, remove plug (b).
* Using the Ohms scale on your multimeter, check the resistance of the excitation winding. Access the excitation winding via the connector where the two yellow wires of the plug connect to it. Each generator size will have a different value for the winding resistance. Check the chart in the graphic for the correct values—use a tolerance of +0.5/-0.0 Ohm.
* If the correct amount of resistance was not measured, replace the stator.
* If the correct amount of resistance was measured, continue.
* Check the excitation winding for resistance to ground. (Measure resistance between the winding and the ground stud of the stator. Measure both sides of the winding.)
> If there is resistance to ground, the excitation winding has failed, replace the stator.
> If there is no resistance to ground, the excitation winding is OK.
Checking AVR’s Sensing Wires—GP 2500A, GP 2600
There are two sensing wires feeding the Automatic Voltage Regulator (AVR) both attached to main winding 2. If the sensing wires are shorted or broken, the AVR will not perform correctly. To check the continuity of the sensing wires, carry out the following procedures:
Stop the engine.
* Remove the two screws which secure the end cover to the generator and remove the end cover.
* Disconnect the generator plug (a).
The two sensing wires are the brown and blue wires that share the same connector (b) as the wires for the DC winding; disconnect this connector.
* Check each wire from the DC winding plug (c) with its counterpart in the generator plug (d): blue to blue; brown to brown. In each case there should be continuity. Also check the wires from the DC winding plug to the generator plug, blue to brown; and brown to blue. In each case there should be continuity.
* If the wires lack continuity in any of the tests, the sensing wires have failed; replace the stator.
* If the wires have continuity in all cases, continue.
Check each wire from the DC winding plug to ground. (Measure between the winding and either the outer metal case of the generator or the ground stud on the frame.)
> If either wire has resistance to ground, it has failed.
> If both wires show no resistance to ground, they are OK.
There are two sensing wires feeding the Automatic Voltage Regulator (AVR), one attached to each of the main windings. If the sensing wires are shorted or broken, the AVR will not perform correctly. To check the continuity of the sensing wires, carry out the following procedures:
Stop the engine.
* Remove the two screws which secure the end cover to the generator and remove the end cover.
* Disconnect the yellow-, red-, black-, and green-marked wires from the generator terminal strip (h).
The first sensing wire, represented by the brown wire on the electrical schematic, is internal to the stator. The AVR connects to this wire at the connection point at the upper portion of the stator. Access the wire by disconnecting the plug (a).
To check the first sensing wire, check for continuity between the connection point (b) where the brown wire from the AVR plug connects and main winding 2 at the terminal strip (c) where the red-marked wire usually connects. There should be continuity.
* If the first sensing wire does not have continuity, replace the stator.
* If the first sensing wire has continuity, continue.
Check the first sensing wire for a short to ground. (Measure resistance between the wire and the ground stud of the stator.)
* If the first sensing wire has resistance to ground, replace the stator.
* If the first sensing wire has no resistance to ground, continue.
The second sensing wire is really a schema. It is represented by the blue wire and then the brown wire on the electrical schematic. This sensing schema runs back through the Voltage Selector Switch (VSS) where the wiring splits, with one wire running to main winding 1, another to main winding 2. The schema is accessed by disconnecting the plug (d) from the connection point at the lower end of the stator. To check the schema, first check the main-winding-2 side. To do so, place the VSS in the 120V position. With one lead of your multimeter, probe the blue wire (e) of the plug. With the other lead, probe the generator terminal strip (f) where the red-marked wire is usually connected. There should be continuity.
* Next, check the main-winding-1 side. To do so, place the VSS in the 120V/240V position. With one lead of your multimeter, probe the blue wire (e) of the plug. With the other lead, probe the generator terminal strip (g) where the black-marked wire is usually connected. There should be continuity.
* If the second sensing wire (schema) does not have continuity, check the wiring through the various connectors and the VSS.
* Repair or replace components as needed.
If the second sensing wire (schema) has continuity, continue.
* Check the blue wire for shorts to ground. (Measure resistance between the wire and the ground stud of the stator.)
If the second sensing wire (schema) has resistance to ground, check the wiring through the various connectors and the VSS.
* Repair or replace components as needed.
*If the second sensing wire (schema) has no resistance to ground, the second sensing wire (schema) is OK.
Confirming a Malfunctioning AVR
By removing the two sensing wires of the regulator and measuring the output voltage of the generator, you can determine if the generator windings and the AVR are functioning correctly. When the sensing wires are removed from the schema, the generator should produce high voltage (greater than 150V, usually around 180V). If this high voltage is still produced with the AVR’s sensing wires connected, the AVR is malfunctioning. To check the AVR, carry out the following procedures:
* Stop the engine.
* Place the auto idle switch in the OFF position.
* Remove the two screws which secure the end cover to the generator and * remove the end cover.
* Disconnect plugs (a and e).
* Create two short jumper wires (b and c) each with one male spade and one female spade. Connect the jumpers between the yellow wires of the plug (e) and where the yellow wires connect to the stator.
NOTE: Be sure to connect the jumper wires correctly. Damage to the generator may occur if the wires are incorrectly connected.
* Start the engine and check the voltage at the terminal strip between the wire with the yellow marking and the wire with the red marking.
There should be approximately 180V. Also check between the wire with the green marking and the wire with the black marking. There should be approximately 180V.
If approximately 180V is not measured, the generator winding may be bad. See section Checking Main and Rotor Winding. If approximately 180V is measured, the generator winding are functioning properly, but the AVR is not. Replace the AVR.
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