43 Calibrate Sensors

Placement and Calibration of Sensors

Calibrate Sensors

CHAPTER

4

Placement and Calibration of Sensors

Before you begin your measurement sampling, it is recommended to calibrate the sensors you will be using. This chapter focuses on inserting and removing sensors, calibrating each sensor, viewing past calibrations, and how to verify your calibration set points. (Reference the following sections which apply to your installed sensor components.)

Calibrating sensors include:

 Particulate sensor

 Pump flow rate calibration

 CO

2

and O

2

sensor

 Toxic sensors

 Photo-Ionization Detector (PID) sensor (for VOCs)

 Temperature (temp) and Relative humidity (RH) sensors

Inserting and Removing Sensors

1.

The sensors you purchased with your EVM will be inserted, factory calibrated, and ready for usage.

To understand how to insert or replace a sensor this is discussed in the procedures below.

 NOTE

: To order new sensors when expired, see Appendix A , Replacement and optional parts.)

 Inserting sensors

2.

Ensure the instrument is turned off and the external power cord is disconnected. Next, remove the sensor bar by unscrewing two screws from the top compartment with a screw driver.

3.

Lift the cover off and set aside. (The location of the sensors is indicated in Figure 4-2.)

4.

Remove the black manifold casing.

Manifold

Sensor housing

Figure 4-1: Sensor housing and manifold

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44 Placement and Calibration of Sensors

Calibrating Particulates

5.

To insert a sensor, gently push the sensor’s pins into the socket pin of the circuit board so it aligns accordingly. It will fit securely.

6.

To remove a sensor, pull the senor up horizontally and remove it from the sensor chamber.

7.

When completed, replace the black manifold over the sensors and then place the cover over the sensor housing. Tighten the screws back into place.

Air inlet cover

Screw 1

Dial-in Impactors

Toxic sensor

Sensor bar- Remove screw 1 & screw 2 and lift off cover.

Temperature/

Relative Humidity sensor

(Dry bulb thermometer measures ambient air temperature)

Screw 2

PID sensor

CO

2

Sensor

Figure 4-2: Sensors’ locations

 NOTE: The Temperature/ Relative Humidity sensor is not user removable.

 NOTE: The user will receive a message on the display when a new sensor is detected or an existing sensor is no longer detected.

Calibrating Particulates

The EVM is factory calibrated to the “Arizona Road Dust” (also called “ISO Road dust” ISO 12103-1 A2

Fine) standard.

Before you measure particulates, it is recommended to calibrate to the environment you are in. If you are in an ARD environment, you would adjust the impactor to correlate with a specific particulate setting, run a calibration based on the particulates in that environment, and compare the results against the

ARD calibration. If you are in any other environment, you would calibrate based on the environment you are in by determining a correction factor (also called “K-factor”) to the correct variation from the ARD calibration standard.

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45 Placement and Calibration of Sensors

Impactor and use

The EVM supports eight different user profiles. Each profile stores a customizable profile name field, and a correction factor. (Setting-up profiles/correction factors is discussed in the Set-up chapter,

“Setting profiles for particulates”).

The following sections will walk you through how the impactor operates, how to adjust the impactor, how to run a zero calibration, and lastly running a gravimetric calibration.

Impactor and use

The impactor is a device used to remove larger sized particulates from the air-stream you are measuring.

How does it operate?

Air travels through the impactor and the heavy particulates will stick to the greased plates within the impactor (1). The Pump will circulate the air as it passes through the tubing in the back of the instrument (2). The smaller, lighter particulates will pass through the optical engine (3) and collects in the gravimetric filter/cassettes (4).

2. Pump – circulates the air through the tubing

1. Filters through impactor

3. Passes through optical engine

4. Collects in Grav. filter/cassettes

Figure 4-3: How the impactor functions

 NOTE: Depending on the environment (i.e., a dense, dusty manufacturing plant), you will want to ensure the impactor is well greased and cleaned before using. Additionally, it is recommended to monitor this process while measuring. You may need to stop your measurements, clean and grease the impactors, and then resume measuring. To clean and

grease the impactors, see Chapter 7 “Cleaning and maintenance”.

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46 Placement and Calibration of Sensors

Adjusting the Impactor/Turret Setting

Adjusting the Impactor/Turret Setting

When measuring, the industrial processes (such as sanding, cutting, crushing, grinding, and transportation) cause air pollutants. The size of the particles will enter the human body in different areas, affecting the nasal, throat, and/or lung area.

The impactor setting is used to trap and filter out the larger size particles based on your cut-point (or impactor setting). The range is programmed between 1 μm to over 100 μm. For example, if you are measuring coal dust (aimed at the lung area), you would adjust your impactor setting to PM10. The following are the user-selectable cut-points:

 PM2.5, PM4, PM10, or PM (all dust ranging from 0 μm-100 μm)

 NOTE: The particulate size is written on top of the turret. For PM there is no marking but is noted by the (raised) air chamber.

 Adjust impactor/turret for particulate logging

1.

Using the keypad navigate to the particulate or composite measurement screen.

 How to?

From the Start screen, press the Right arrow key.

PM 2.5 & profile displayed

Impactor setting updates as the turret is rotated

(when in stop mode)

Figure 4-4: PM2.5 impactor setting example

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47 Placement and Calibration of Sensors

Particulates Calibration (Zero Cal)

2.

Twist the turret (red casing around the impactor) to the left or right until you see the appropriate setting on the display. It will align to the impactor text and arrow on top of the housing.

 NOTE: The actual diameter of the air inlet hole is directly to the left of the impactor text positioning.

Air inlet hole for PM2.5 Air inlet hole for PM4

PM2.5 position

Air inlet hole for PM10

PM4 position

Air inlet hole for PM

PM10 position PM position (no text marking)

Position used for zero calibration

Figure 4-5: Adjusting impactor/turret setting

3.

If you see “ < > PM ERR ”, this indicates the impactor is not in the correct position and that it is between two positions. Adjust the turret, until the correct reading is displayed on the screen.

Particulates Calibration (Zero Cal)

A zero calibration is recommended the first time you measure particulates in the run mode. For particulate calibration, place a zero filter (also called a

HEPA filter) with attached coupler into the vent of the turret. The impactor setting must be set at PM in order to conduct a zero cal.

 NOTE: For the span on the particulate calibration, refer to the

“Gravimetric Filtering” instructions to determine the gain factor from the correction factor.

 Particulates zero cal

1.

Insert the attached coupler and zero filter into the turret. Ensure the impactor is well-greased

before calibrating which requires a thin film of grease. (See “ Impactor care ” for details).

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48 Placement and Calibration of Sensors

Particulates Calibration (Zero Cal)





Zero/HEPA filter

Used for particulate zero cal.

Zero filter with coupler and vent opening

Insert the Zero Filter via the coupler into the “2.5” vent opening.

Turret

Turn the turret so “PM” appears on the display of the EVM. The raised section will align with the

“impactor” text.

Figure 4-6: Particulate zero cal with HEPA filter

2.

Adjust the turret/impactor to PM (refer to “Turret” in Figure 4-6).

3.

From the Start screen, press ▲ / ▼ Arrows until Calibration is selected and press Enter .

Calibration – select to open to the Calibration set screen

Figure 4-7: Selecting calibration screen

4.

In the Calibration screen, press ▲ / ▼ Arrows and select PM (for particulate matter).

 NOTE : If the impactor setting is incorrect, the instrument will flash a warning sign indicating that you need to turn the impactor to “PM” before proceeding.

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49 Placement and Calibration of Sensors

Particulates Calibration (Zero Cal)

5.

Press the Cal soft key. (The pump will turn on.)

 NOTE: The HISTR and VERIFY soft keys will not be present if a user calibration and a calibration verify have not been performed.

PM

History soft key

Calibration soft key

Verify soft key

Figure 4-8: Particulate cal screen

6.

The ready screen with the PM, Profile will appear. Press the Start soft key.

Start soft key

Figure 4-9: Particulate calibration and ready screen

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50 Placement and Calibration of Sensors

Particulates Calibration (Zero Cal)

7.

Allow the level to stabilize (approximately 1–3 minutes). It will state Waiting (A) and Set soft key will appear when it has stabilized (B).

A B

Zero will appear when it has stabilized

Current Level reading

Set soft key will appear when stabilized

Figure 4-10: Particulate calibration and waiting screen

8.

Press the Set soft key to set the Zero cal point.

9.

The instrument will show a Pause state with the intended and actual values.

Save soft key

Figure 4-11: Particulate calibration pause screen

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51 Placement and Calibration of Sensors

Particulate Advanced Calibration (Gravimetric)

10.

Press the Save soft key to save your calibration (or press Cancel and Retry to repeat this process.)

A screen pop-up will state “Zero cal set point” when completed (or “User canceled calibration”). A pass (cancel) screen will be displayed.

Retry

Actual calibration value

Exit

Figure 4-12: Zero Cal set for Particulates

 Press Retry soft key to repeat the zero cal procedures.

11.

Press Exit soft key to close this screen. To return to the start screen, press On/Off/Esc or press the Cal soft key to continue calibrating the sensors.

 NOTE: A zero cal is performed for the instrument and will be used for all profiles.

Particulate Advanced Calibration (Gravimetric)

With the EVM, you can store up to eight different profiles (also called correction factors) to reflect the environment or building zone you plan to measure.

The instrument is factory calibrated to Arizona Road dust. In some situations, you may want to perform a gravimetric calibration in order to determine the correction factor for an alternative environment. This is an optional procedure.

 NOTE: If you do not plan on performing an advanced particulate calibration with gravimetric sampling.

With a gravimetric calibration, you determine the mass of the particulate you want to measure. The particulate mass is then used to calculate a correction factor to the environment you will be measuring.

The steps below outline a gravimetric calibration.

(For additional specifications on a gravimetric calibration, please refer to the NIOSH 0600 standard.)

EVM Series User Manual