Casella-cel Apex personal sampling pumps Instrukcja Użytkownika Pobierz pdf (Strona 19)

For example, when 10 litres must be sampled over an 8-hour work shift, the pump flow can be set to run

at a flow rate of:

= 0.021 litres / min = 21 millilitres / min

8 x 60

For the whole shift, which is a very low flow.

1 min

02011

Run: 480 min

Exp: 10 min

TWA: 2%

Off

47 min

Off

47 min

Off

47 min

Off

47 min

Off

47 min

Off

47 min

Off

47 min

Off

47 min

Off

47 min

Off

47 min

Alternatively, the TWA mode can be used to run the pump for short periods at a higher rate, for example 1

l/min, with the pump actually running for only:

= 10 minutes

during 8 hour shift

Using TWA mode, the sampling (RUN) time should be set to 8 hours

and the pump-on exposure (EXP) time to 10 minutes, as follows.

1. Enter Configuration Mode, select Program Mode / ON and accept it

as described in Section 2.4.

The instrument reverts to Hold Mode.

2. Press or several times until TWA blinks on the display.

3. Press to select it.

RUN is displayed and the run time blinks to indicate that it can be

changed.

4. Use or to select a run time.

Sampling (RUN) durations between 3 minute and 1 hour can be set

in 1-minute steps and durations between 1 and 25 hours in 10-minute steps.

5. Press to accept the selected run time.

EXP is displayed, and the exposure time blinks to show it can be

changed.

6. Use or to select an exposure time.

The available range is from 2 minutes to “1 minute less than the run

time“, in 1-minute steps.

7. Press to accept an exposure time and start sampling.

In addition to the usual and symbols, the display shows PROG. to indicate that a program

is active.

The pump ON-times are fixed at 1 minute, and the instrument calculates the necessary OFF-times

to spread these 1 minute intervals evenly throughout the run time.

While the program is running, the display cycles through current accumulated run time, volume

sampled, air temperature and calculated TWA (as a percentage of run time).

During OFF-times (pump not running) the and symbols are displayed to show the

instrument is paused.

Once the run is completed, the pump will switch OFF and the display show the symbol and a

PROGEnd message.

Figure 10: TWA ON/OFF cycle

1 2 ... 14 15 16 17 18 19 20 21 22 23 24 ... 39 40

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Casella-cel Apex personal sampling pumps Instrukcja Użytkownika Strona 19

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