Hach SIGMA 900 User Manual download pdf (Page 26)

Page 26

Measurements Triggered by Liquid Levels or Flow

8544operations.fm

Section 4

5. To exit the manual mode, press CLEAR ENTRY. This returns the sampler

to the standby state.

While the sampler is in standby, a sample cycle can be initiated by pressing

the

TAKE SAMPLE key.

4.8 Measurements Triggered by Liquid Levels or Flow

The sampler can operate in any one of three control modes, using an external

controlling device (i.e. Liquid Level Actuator, Cat. No. 943, or an external flow

meter). In any of the three modes, the sampler remains in a standby state until

liquid at the sample source reaches a predetermined level. This feature may

be also used to access the setup of the storm water monitoring program, First

Flush. The three modes are described below:

Mode 1

The instrument collects a sample within the first minute that the liquid rises to

the predetermined level. After the first sample is taken, the sample interval

automatically resets to the programmed interval.

If the liquid falls below the predetermined level, the sampler continues

collect samples at the programmed time or flow interval, until the

program

ends.

Mode 2

The instrument collects a sample within the first minute that liquid rises to the

predetermined level. After the first sample is taken, the sample interval

automatically resets to the programmed interval. The sample program ends if

liquid falls below the predetermined level. If the liquid again rises to the

predetermined level, a sample is taken within the first minute and the interval

automatically resets to the programmed time or flow interval.

Mode 3

When the liquid rises to a predetermined level, a sample is not taken

immediately. A sample is taken only when liquid is at or above the

predetermined level and after the programmed sample interval has elapsed.

The interval between samples counts down and resets even when the liquid

level is below the predetermined (actuation) level. This mode is used to

synchronize sample collection with a real-time clock when sampling in the

time mode.

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Hach SIGMA 900 User Manual Page 26