Reliability of measurement results can be ensured by regular self-tests which the 1312 performs. Accuracy is ensured by the 1312’s ability to compensate any measurement for temperature fluctuations, water-vapor interference and interference from other gases known to be present. 
The monitoring system is easily operated via a PC, or via the front-panel pushbuttons when using a stand-alone instrument configuration. Short explanatory text guide the user through each operating procedure. Therefore, no special training is required to operate the 1312. 

The 1312PC software enables the user to calibrate the monitor and load the user-defined measurement setups prior to monitoring. During a monitoring task, real-time measurement data is presented on screen as both graphs and tables, and the data is stored in named databases. When a monitoring task is completed, the 1312PC software can assist in analyzing the data. The measurement data
stored in the databases is easily accessible, and can be displayed on screen, printed out, and exported to other spreadsheet, database and word processor programs when required. 

If a stand-alone configuration is required, the monitor can be operated using the front panel push-keys, The measurement results are stored in the monitor's memory, and can be uploaded to the PC or printed at a later stage. 

The 1312 has a sturdy, dust-proof casing to protect its components. It is portable, and requires no warm-up time or re-calibration after moving – making it ideal for short-term monitoring of air samples drawn from its immediate environment. For long-term monitoring the 1312 is placed indoors and collects air samples for analysis, via tubing, from points up to 50m away. 

Read about the many applications for the 1312

Read how the 1312 Photoacoustic Monitor Helps BASF Manage Ethylene Oxide Levels here

SELECTIVITY 

The selectivity of the 1312 is determined by the optical filters installed in it’s filter carousel. A wide range of narrow-band optical filters is available from Innova AirTech Instruments. By studying the absorption spectra of the gases to be monitored, as well as those of any other gases, which may be found in the ambient air in the same area, the most appropriate optical filters can be chosen. Please refer to the Gas Detection Limits chart for details. 

Water vapor, which is nearly always present in ambient air, absorbs infrared light at most wavelengths so that, irrespective of which optical filter is used, water vapor will contribute to the total acoustic signal in the analysis cell. The higher the concentration of water vapor in the cell, the more it contributes to the measured signal. However, a special optical filter is permanently installed in the filter carousel of the 1312, which allows water-vapor’s contribution to be measured separately during each measurement cycle. The 1312 is thus able to compensate for water-vapor’s interference. 

Any other interfering gas, which is known to be present in the ambient air, can be compensated for in a similar fashion. By installing an optical filter to selectively measure the concentration of the interferent gas, the user can setup the 1312 to compensate for the interferent gas’s contribution. 

CALIBRATION 

After the relevant optical filters are installed, the monitor must be calibrated. Four types of calibration are available: zero-point, humidity-interference, humidity-span and gas calibration. Regardless of the calibration type, the 1312PC software makes it easy. Setting up the calibration is done via the familiar Windows 95 environment. The raw measurement data from the monitor is transferred to the PC where it is displayed graphically. Using the cursors in the graphic window, the best ranges can be defined. The raw data in these areas is used to produce the offset calculation values to enable humidity interference cross-compensation. Only when you are satisfied with the result, are these calculation values downloaded to the monitor. 

Due to the 1312’s high stability (low drift), calibration is seldom necessary more than four times a year. 

OPERATION 

The 1312 monitoring system is easy to operate, either directly via a PC or via the push-keys on the monitor’s front panel. This enables the monitor to be operated as both an on-line and stand-alone instrument. 

You define all the information necessary to start a monitoring task. The PC uses menu bars and "index-card" labeled windows to divide the procedures in to logical sections. The front panel pushbuttons are supported by short explanatory texts, guiding the operator through the procedures. 

Setting-Up the Monitor 

Each monitoring task is given a distinct name. Under this name, the setup option enables you to define all the parameters necessary for the monitoring task to be completed. The Sample Integration Times (S.I.T.) are defined here. This allows you to decide the measurement accuracy against the speed of the measurements. The monitor can be set to measure at one of the seven different S.I.T.s (from 0.5s to
50s). The shortest S.I.T.s enable many measurements to be made quickly where the accuracy of the results are not crucial, while the longest S.I.T.s can be selected for each filter. 

This setup option also enables you to select if cross-compensation for known interferents and water vapor should occur, as well as decide on the sampling mode (continuous or fixed time interval). The flushing time is also set here. You decide whether only the measurement chamber is flushed, using a minimal gas sample, or whether the chamber and sampling tubing should be flushed and the length of
time this should take. Alternatively, the monitor can be set to find the optimal flushing time, automatically. 

Should some form of warning be necessary, the software enables the user to set minimum and maximum alarm trigger levels for each measured gas. It is also possible to define what action is taken when an alarm is triggered. 

Starting Measurements 

Once the setup parameters have been defined, measurements can be started immediately. Alternatively, a delayed start time can be defined. The PC and the monitor have synchronized clocks, so whether the monitor is operating on-line or stand-alone, the measurements will start at the correct time. The monitoring task will continue until it is stopped manually, or a stop time can be defined, enabling the system to run completely unattended. 

Memory Mode 

This option is available when the monitor is operating as a stand-alone instrument. During a monitoring task all results are stored in a memory called Display Memory. While operating Memory mode, data in this memory can be copied into the 1312’s other memory (Background Memory) to prevent it being overwritten by results from the next task. 

Data stored in Background Memory can be recalled to Display Memory and then can be uploaded to a PC. 

Alarms 

When on-line measurements are being made, the software enables the user to set trigger, minimum, and maximum alarm levels for each measured gas. It is also possible to define what action is taken when an alarm is triggered. 

MEASUREMENT RESULTS 

On-line Measurements 

Measurements results are transferred directly to the PC. Here they can be displayed on screen as real-time values in tables and graphs. The graphs can be set up to display only the desired gases, within defined concentration ranges and results from statistical analyses. 

Regardless of what is displayed on screen, all measurement data is stored in user-defined databases, in a MS-Access format. This makes results readily available to view at a later stage for further analyses, or for inclusion in other programs, for example, Excel or Word. The 1312PC software, with its Open
Database Connectivity (ODBC), enables result data to be utilized by any programs using this form of data exchange. 

Stand-alone Measurements 

Gas-measurement results are displayed on the 1312’s screen as soon as they are available, and are constantly updated. During a task, the 1312 performs a running statistical analysis of measured gas concentrations, calculating for each monitored gas: the Mean Value; the Standard Deviation; and the Maximum and Minimum measured concentrations. The Mean Value is the same as the Time-Weighted
Average (TWA) value during the total monitoring period. 

The individual results stored in Display Memory can also be automatically averaged and presented on the display. 

Measurement data stored in the 1312’s Display Memory can be printed out in list form on any standard test-printer, via the IEEE488 or RS-232 interfaces. 

If any interesting or unusual event occurs during a monitoring task, the measurement being performed at this time can be "marked". This enables the user to assess the event’s affect on the monitoring task. 

When the monitor is once again connected to a PC, all the measurement results can be uploaded. These can then be viewed and used similar to the on-line gas measurement results. 

Exporting Data 

If measurement results need to be used by other instruments in the process, or by programs which can not use ODBC, data can be exported as semicolon delimited ASCII files. 

RELIABILITY 

Reliability can be ensured by a series of self-tests that the monitor can perform. The self-tests, which can be disabled if required, check software, data integrity, and the components of the 1312 to ensure that they function properly. If any fault is found, it is reported in the measurement results so that users can see what, if anything, has affected the accuracy of the measurement. 

If there is an AC mains power-supply failure, the 1312 will automatically startup again when power is restored. Measurement data is stored in the monitor's memory and can be uploaded to the PC when the software has been restarted. 

MAINTENANCE 

The only maintenance tasks necessary are calibration and changing the filters in the internal and external air-filtration units of the 1312. Both tasks are easily performed, and are typically necessary only four times a year. 

OTHER REMOTE CONTROL OPTIONS 

Innova AirTech Instruments also offers two additional application software programs, application Software Type 7620. 

Using the Type 7300, a computer can remotely control a 1312 together with one Multipoint Sampler Type 1309 for sequentially monitoring air-samples from up to 12 locations. 

Using the Type 7620, a computer can control a 1312 together with up to two Type 1303 Multipoint Sampler and Doser Units. This enables up to 12 locations to be dosed with a tracer-gas and air-samples to be drawn from each location for analysis by the 1312. The software uses the resultant measurements to calculate the air-change or ventilation efficiency of each location. 

SPECIFICATIONS 

Warning! The 1312 must not be placed in areas with flammable gases/vapors in explosive concentrations, or be used to monitor explosive concentrations of these. Also, monitoring of certain aggressive gases, or a very high concentration of water vapor, could damage the 1312. Please contact us for more information.

All terms relating to gas analysis are in accordance with the definitions set out in the ISO International Standard 8158 

Your local Innova representative will assist in the selection of suitable optical filters. Details are provided in the "Optical Filters" Product Data Sheet and the Gas Detection Limits wall-chart. 

MEASUREMENT SYSTEM OF THE 1312 

Measurement Cycle 

1.The pump draws air from the sampling point through two air-filters to flush out the "old" air in the measurement system and replace it with a "new" air sample. 

2.The "new" air sample is hermetically sealed in the analysis cell by closing the inlet and outlet valves. 

3.Light from an infrared light source is reflected off a mirror, passed through a mechanical chopper, which pulsates it, and then through one of the optical filters in the filter carousel. 

4.The light transmitted by the optical filter is selectively absorbed by the gas being monitored, causing the temperature of the gas to increase. Because the light is pulsating, the gas temperature increases and decreases, causing and equivalent increase and decrease in the pressure of the gas (an acoustic signal) in the closed cell. 

5.Two microphones mounted in the cell wall measure this acoustic signal, which is directly proportional to the concentration of the monitored gas present in the cell.
 
6.The filter carousel turns so that light is transmitted through the next optical filter, and the new  signal is measured. The number of times this step is repeated is dependent on the number of gases being measured. The response time is down to approx. 13s for 1 gas or water-vapor, or approx. 40s if 5 gases and water vapor are measured. 

MEASUREMENT TECHNIQUE: Photoacoustic infrared spectroscopy

RESPONSE TIME: (including chamber flushing) is dependent on the sample integration time (S.I.T.) and the flushing time defined. The fastest response time for one gas is 13 s and for 5 gases and water vapor 40s, but see the examples below: (including chamber flushing) is dependent on the sample integration time (S.I.T.) and the flushing time defined. The fastest response time for one gas is 13
seconds; and for 5 gases and water vapor 40 seconds, but see the examples below:

MEASUREMENT RANGE:
Detection Limit: gas-dependent, but using the "Detection Limit Chart", the limits can be calculated using the following multiplication factors. 

Note: an individual S.I.T. can be selected for each filter Dynamic Range: five orders of magnitude (i.e. upper limit=100,000 times the detection limit). To measure over this wide dynamic range, span-calibration must be performed with two different gas concentrations.

MEASUREMENT UNITS: (1312PC) - mg/m3, g/m3, u/m3 ppm, vol%, ppb

ACCURACY:
Zero Drift: Typically ± Detection limit per 3 months
Influence of temperature : ± 0.5% of detection limit / °C
Influence of pressure : ± 0.5% of detection limit /mbar
A concentration of 100x detection limit was used determining these specifications:
Repeatability: 1% of measured value·
Range Drift: ± 2.5% of measured value per 3 months·
Influence of temperature : ± 0.3% of measured value/° C
Influence of pressure : -0.01% of measured value/mbar
Reference conditions:
Measured at 20° C 1013 mbar, and relative humidity (RH): 60%
Measured at 1013 mbar, and RH: 60%
Measured at 20° C and RH: 60%
Measured detection limit is @5s S.I.T.

INTERFERENCE:
The 1312 automatically compensates for temperature fluctuations in its analysis cell, and can
compensate for water vapor in the air sample. If an optical filter is installed to measure a known
interferent, the 1312 can cross-compensate for the interferent

DATA STORAGE CAPACITY:
(for stand-alone) Dependent on the number of gases being measured. Sufficient for a 12-day monitoring task, monitoring 5 gases and water vapor every 10 min.

GENERAL:
Dimensions:
Height: 175mm (6.9 in)
Width: 395mm (15.6 in)
Depth: 300mm (11.8 in)
Weight: 9 kg (19.8 lbs.)
Maximum Pumping Rate: 30cm3/s (flushing sampling tube) and 5cm3/s (flushing measurement chamber)

Power Requirement: 100-127V and 200-240V (50-400Hz) ± 10% AC. Complies with IEC536 Class 1 Safety Standards

Power Consumption: -100VA Alarm Relay Socket: for connection to one or two alarm relays (visual/audio). Alarm levels for each gas are user-defined.

Acoustic Sensitivity: not influenced by external sound.

Vibration Sensitivity: complies with IEC 682-6. Strong vibrations at 20Hz can affect the detection limit.

Back-up Battery: 3V lithium battery, lifetime 5 years. This protects data stored in memory, and powers the internal clock.

COMMUNICATION: The monitor has an IEEE 488 and an RS-232 interface, for data exchange and remote control of the 1312. The 1312PC communicates using the RS-232.

1312PC SOFTWARE: Supplied on 3.5 inch disks

COMPUTER REQUIREMENTS:
Hardware: 
A 486 (50MHz) processor or better
Min. 16Mbytes of RAM
Min. 40Mbytes of space available on the hard disk
VGA monitor or better
One RS-232 port
Mouse
Software: Windows 95

COMPLIANCE WITH STANDARDS:

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Environmental Analytical Systems
286 Mask Island Drive
Barry's Bay, Ontario, Canada K0J 1B0

Phone: 613 756 0101
Toll Free (Canada only): 1 800 427 8591
Fax: 613 756 0909
email: info@enviro-analytical.com

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