Teledyne BDS-3000 - Oxygen analyzer - Manual (Page 71)

Oxygen Analyzer Operation
Teledyne Analytical Instruments 57
• Once the parameters for alarm 1 have been set, press ALARMS
again, and repeat this procedure for alarm 2 (AL–2).
• To reset a latched alarm, go to Dft– and then press either D two
times or Ñ two times. (Toggle it to Y and then back to N.)
–OR –
Go to Ltch – and then press either _ two times or _ two times.
(Toggle it to N and back to Y).
Alarm Hysterisis: There is alarm hysterisis to prevent chatter of
the alarm contacts. It is set to 0.2 ppm for alarms set above 1 ppm, and
10 ppb for alarms set below 1 ppm.
4.6 The Range Function
The Range function allows the operator to program up to three
concentration ranges to correlate with the DC analog outputs. If no
ranges are defined by the user, the instrument defaults to:
Low = 0–100 ppb
Med = 0–1 ppm
High = 0–10 ppm.
The Model BDS 3000 is set at the factor y to default to autoranging. I n
thi s mode, the microprocessor aut omatically r esponds to concent ration
changes by swit ching ranges for optimum readout sensitivi ty. If the current
range lim its ar e exceeded, the instrument wil l automatically shift to the next
higher range. I f the concentration fall s to below 90% of full scale of the
next lower range, the instr ument will switch to that range. A corresponding
shi ft in the DC percent-of- range output , and in the range ID outputs, will be
not iced.
The autoranging feature can be overridden so that analog output
stays on a fixed range regardless of the oxygen concentration detected. If
the concentration exceeds the upper limit of the range, the DC output
will saturate at 1 VDC (20 mA at the current output).
However, the digital readout and the RS-232 output of the
concentration are unaffected by the fixed range. They continue to read
accurately with full precision. See Front Panel description in Chapter 1.
The automatic fourth range is always 0-1000 ppm and is not
programmable.