Murco MGS Instrukcja Użytkownika Pobierz pdf (Strona 3)

7- Tighten on the ampoule until it shatters allowing the contents to diffuse

in the beaker. It should be left in place for approximately 5 min.

8- Voltage output will increase. This confirms that the sensor is

responding. In the case of an ampoule quantified test a response

equivalent to at least 50% of the test gas will confirm that the system

is in order.

9- Carefully remove any ampoule remains from the gas detector and

beaker.

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Remove the enclosure lid of the gas detector (not in an Ex area).

Connect voltmeter to monitor sensor response, monitor 0-10V (Jumper

JP1 and JP3 off) response on CON 2 between pins OV & V.

Expose the sensor to gas from the cylinder. You can place the entire MGS

into a plastic bag or use a plastic hose/hood to direct gas to the sensor

head. A response of above 80% is acceptable.

33-- CCAALLIIBBRRAATTIIOONN

This is the adjustment of the gas detector’s accuracy or recalibrating after

sensor element exchange using calibration gas.

Murco offers a calibration kit that consists of a Calibration gas cylinder, a flow

regulation valve with flexible non-absorbant tubing and vented calibration hood.

Tools required:

1- Gas can with the appropriate gas and concentration

2- A voltmeter- crocodile clips recommended

3- Estimate 30 min per sensor

The MGS has three sensor PCB versions: SC, EC, IR.

Calibration and alarm relay set point is done on a 0-5V scale.

Adjusting the alarm relay

This process is the same for all versions. See diagram 2 and 3 for location of pot

P1 and test points 0V and REF1.

The first step to setting the alarm relay at the desired levels:

1- Pot P1 is used to adjust the set point at which the relay activates. Monitor

the output between test points 0V (negative) and REF1 (positive). See

example below.

Example

: For a range of 0-1000ppm, relay @ 100ppm

Relay = 100 ppm x 5 so that Alarm relay = 0.5 Volts

1000

while the 0-5V output sensor signal corresponds to 0-1000 ppm range.

Sensor PCB

– adjusting the detection range

1- Semiconductor Sensor (SC)

(see Diagram 2)

There are two adjustments required: the zero and the span. They are monitored

at 0V and VS on a 0-5V scale. If the target range is 0-1000ppm, and the gas

used is 1000 ppm then

5V=1000ppm.

1.1- Pot P2 is used to adjust the

zero of the range (span).

Monitor the output between

0V (negative) and VS

(positive) and adjust the Pot

to 0 V or slightly positive

(0.01 V is acceptable).

2.2- Pot P3 is used to calibrate the

range (span) of the sensor.

Monitor the output between

0V (negative) and VS

(positive). Expose the sensor

to calibration gas and allow to

stabilise and adjust pot P3 to

5V.

2- Electrochemical Sensor (EC)

There are two adjustments required: the zero and the span. They are

monitored at 0V and VS on a 0-5V scale. If the target range is 0-1000ppm,

and the gas used is 1000 ppm then 5V=1000ppm.

3- Infrared (IR)

(see Diagram 3)

3.1- Pot VR202 is used to adjust the zero of the range (span). Monitor the

output between 0V (negative) and VS (positive) and expose the sensor to

Nitrogen or zero air, and once stable, adjust the Pot to 0 V or slightly

positive (0.01 V is acceptable).

3.2- Pot VR201 is used to calibrate the range (span) of the sensor. Monitor

the output between 0V (negative) and VS (positive). Expose the sensor to

calibration gas and allow to stabilise and adjust pot VR202 to 5V.

NOTE:

Sensors outputs are linear, thus as long as you have a gas canister of

known concentration you can calibrate to any desired range.

Example

: For a range of 0-1000ppm, and a canister of the target gas at

800ppm

The 0-5V signal corresponds to 0-1000, thus if using the above canister:

Voltage= 800 ppm x 5 = 4V and so the output voltage signal should

1000

be adjusted to 4V.

44-- AADDDDIITTIIOONNAALL RREECCOOMMMMEENNDDAATTIIOONNSS

FFAALLSSEE AALLAARRMMSS

: If false alarms are being triggered by background gases,

paint fumes, etc, extreme humidity or temperature conditions, you will find

that the zero has moved to a + value, you can adjust the zero setting back to

zero to compensate. You may also increase the response time delay to help

eliminate false alarms.

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Below we show typical time to normalize for various sensor types. The units

are powered up and the output voltage monitored on the 0-10V-output. The

approximate time to drop to near 0V is shown.

Sensor Type Stabilised ~0V

Electro-Chemical 20-30 Seconds

Semi-Conductor 1-3 Minute

Infrared 2 Minute

The electro-chemical sensor on power up outputs a signal voltage normally

below the set alarm level. Semiconductors output over the + max scale i.e. >

5V. Both move towards zero as they stabilise.

If sensors have been in long-term storage or the detectors have been turned

off for a long period, normalisation would be much slower. However within 1-

2 hours sensors should have dropped below the alarm level and be

operational. You can monitor progress exactly by monitoring the 0-10V

output, when the output settles around zero the sensor is normalised. In

exceptional circumstances the process can take up to 24hours or more to get

to 0V, again monitor the 0-10V output and you can see what is happening.

COM

Relay

+ Sounder

REF10V

ZeroSpan

SW2 SW1

LD2 LD1

CN1 CN2 CN3

JP6

JP1

DDiiaaggrraamm 22

Relay and Sounder Delay – JP5 & JP6 off : no delay

JP5 on only : 1 minute

JP6 on only : 5 minutes

JP5 & JP6 on : 10 minutes

JP4 – on : Not used

JP3 – on : 4-20mA or 2-10 Volt output

off : 0-10Volt output

JP2 – on : Sounder enabled

JP1 – on : Divide Voltage output by 2

(0-5 or 1-5 Volt output

off : full 0-10 or 2-10 volt output

Relay Output

4-20mA output

0-5/1-5/0-10/2-10 Volt output

Power

12 to 24V DC

12 to 24V AC

Adjust Span

(Adjust zero in

IR model)

Adjust Zero

(Adjust span in

R model)

Adjust Sounder

and Relay set point

(P1)

ounder & Relay Set

Point Voltage (Ref 1)

Short to Cancel

Warm up Delay

Sensor Voltage (VS)

CN1 CN2 CN3

Jumper for

AC or DC

Electrochemical or IR Sensor

AC DC

SW2 SW1

DDiiaaggrraamm 33

1 2 3 4

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