Super Systems Hydrogen Nitrider Analyzer - Manual (Page 6)

Basic Nitriding Sampling System – Hydrogen Analyzer
Super Systems Inc. Page 6 of 12
Percent Dissociation
Dissociation is derived from the amount of Hydrogen in the sample gas.
Percent Ammonia
The amount of Ammonia can also be inferred from the Hydrogen value.
Nitriding Potential
The accurate calculation of Nitriding Potential (K
N
) requires the flow rates of other gases that are being
introduced into the process. These flow rates are measured in SCFH (Standard Cubic Feet per Hour). K
N
can only be calculated by entering the flow of Nitrogen (N
2
), Ammonia (NH
3
) and % Dissociated Ammonia
(%DA). These values are entered at the bottom of the main screen when K
N
is selected.
Output Configuration
There are two 4-20mA outputs that can be configured for any of the four parameters. For each input, the
operator can select the Source (H
2
, DA, NH
3
, K
N
), the zero value (the value to be represented by 4mA) and
the span value (the value to be represented by 20mA).
• Output 1 can be measured from Terminal #1121(+) and 1111 (-).
• Output 2 can be measured from Terminal #1121(+) and 1131 (-).
Output Calibration
Accurate retransmission of the selected parameters can only be obtained through calibrating both of the
analog outputs. This is done at the factory prior to shipment, however it is a relatively simple procedure
that can be performed in the field if desired. To perform a calibration, a multimeter with a current input
is required. Please keep in mind that the accuracy of the instrument used to calibrate the outputs is
directly related to the accuracy of the outputs after calibration, so a meter calibrated against NIST
(National Institute of Standards and Technology) standards is preferred. Before performing any
calibrations, all other devices must be disconnected from the analog outputs. Multiple devices on the
outputs will cause inaccurate measurement of current.
Attach the leads of the multimeter to the terminals for Output 1. The positive lead should be attached to
Terminal #1121 and the negative lead to Terminal 1111. Select “Zero Output 1” and press the “Prep for
Cal” button. The low limit of the output is 4mA, so 4.000 is shown as the default measured value. Ideally
the meter connected to the outputs will also show 4.000. If the two values are not close enough to obtain
the desired level of accuracy, a calibration should be performed.
If, for example, the meter connected to the outputs reads 4.216mA, then the value “4.216” should be
entered on the screen as the Measured Value. Once the value has been entered, press the “calibrate”
button. This will offset the mA output of the instrument in an amount that results in an exact output of
4.000mA. When the calibration is complete, the multimeter should be reading 4.000mA (+/- .005).
The procedure can be repeated for the Span of Output 1. When “Span Output 1” is selected and “Prep for
Cal” is pressed, the instrument will output the high output limit, which is 20mA. The multimeter will
display the actual output from the instrument, and if it is not within the desired tolerance it can be
calibrated using the same procedure as above.
To calibrate Output 2, attach the leads of the multimeter to Terminal #1121 (+) and the negative lead to
Terminal 1131 (-) and follow the same procedure that was used for the first output.
Sensor Calibration
A proper calibration of the sensor requires two gases. The first gas should be pure Nitrogen or Argon.
This contains no Hydrogen, and is therefore referred to as the Zero Gas. The second gas is the Span Gas.
The Span Gas should ideally contain a quantity of Hydrogen similar to the amount of Hydrogen in the
process gas. The Span Gas should also include any other gases that are present in the process gas in