Introduction To Tvoc - ION TVOC Instrument User Manual

TVOC MANUAL
2

Introduction to TVOC

TVOC is a fixed continuous monitor for the detection and measurement of total volatile organic compounds,
which can be dangerous from both a poisoning and explosive perspective. Total VOC's are detected using
PID (Photoionisation Detection) technology.
TVOC has a number of user selectable features which define its operation and will be application
dependent. The user can define the detection ranges or 0.01 - 10ppm, 0.1 – 100 ppm or 1 – 1,000 ppm
(Default); detection units, either ppm or mg/m
instrument takes a measurement. Duty cycles are explained in more detail on page 10, TVOC set up, and
page 15 Operation.
IMPORTANT: TVOC can be calibrated on alternative gases to Isobutylene however to ensure TVOC
remains within specification, the correct concentration for the alternative gas must be chosen.
Example: Benzene gas has a response factor of 0.5 which means only half as much concentration is required
to produce the equivalent to Isobutylene.
The ideal gas / concentrations used to set the calibration SPAN are shown below:-
10 ppm range
100 ppm range
1,000 ppm range
How to calculate alternative concentration of gases for gases other than Isobutylene:-
Benzene
Isoprene
Isobutylene
Carbon Disulphide
Ethyl Acrylate
For other gas response factors please refer to the Ion Science web site or contact Ion Science Ltd.
http://www.ionscience.com/GasSearch/tabid/87/Default.aspx
WARNING: Ignoring these guide lines may result may result in calibration failure, loss of resolution or loss
of range.
The default settings of TVOC are:
Detection range
Units
Duty cycle
TVOC gives a continuous 4 – 20 mA output which can be integrated into a DCS control system to give an
indication of VOC levels in the operating environment.
In addition to the 4 – 20 mA output TVOC has an LCD display showing gas concentration and 4 colour LED's.
LED functions are as follows:
Green
Red
Yellow x 2
Please see page 18Calibration for more information on LED status.
Lower limit
8 ppm
90 ppm
90 ppm
Ideal response
for Isobutylene
100
100
100
100
100
– 0.1 – 1000 ppm
- ppm
- 5 seconds ON / 55 seconds OFF
- is an indicator of TVOC's working status
- is the fault indicator
- are calibration status indicators
3
; and the duty cycle time i.e. the frequency that the
Upper limit
12 ppm
110 ppm
110 ppm
Response factor
x 0.5
x 0.7
x 1.0
x 1.4
x 2.0
Page 6 of 28
Ion Science Ltd
Isobutylene equivalent
Isobutylene equivalent
Isobutylene equivalent
Ideal calibration gas
concentration
= 50 ppm
= 70 ppm
= 100 ppm
= 140 ppm
= 200 ppm