RITTER »MultiGas« Ultraviolet Module NDUV / H2S

Table of Contents

Description

The H2S sensor works according to the principle of non-dispersive UV absorption (NDUV). The measuring wavelength used is in the lower nanometer range, which enables interference-free measurements with water vapour and hydrocarbons. This makes the sensor ideal for use in biogas measurements, as accompanying gases such as NH3, CO2, CH4 and H2O do not affect the accuracy of the measurements.

In contrast to photometric NDUV sensors the lifetime of  electrochemical sensors for measurement of H2S is limited. Please note that lifetime data for such sensors are given for air and not for measurement of H2S. For H2S concentrations > 200 ppm the lifetime is reduced, for concentrations > 1000 ppm critical. While the measurement performance of UV-LED is constant, EC sensors are becoming »deaf«.

Applications

  • Biogas analysis
  • Environmental and Process Measurement
  • Leakage detection
  • Industrial gas analysis
  • Renewable Gas Monitoring

Specifications

General features
Measurement technology:Innovative NDUV Sensor
(non-dispersive ultraviolet sensor)
Dual beam
Detectable gases:
SO2 H2S
Number of simultaneously detectable gases:max. 2
Measurement ranges:See Table of Measurement Ranges
Flow rate range:5 ~ 300 ltr/h
For higher flow rates the sensor can be operated in bypass
Max. gas inlet pressure:300 mbar
Pressure loss (without additional optional sensors):10 @ 100 / 35 @ 200 / 70 @ 300 (mbar @ ltr/h)
Temperature compensation:Yes
Data acquisition software:Yes
Lifetime of UV radiation source:> 8 000 h
Measurement cuvette:Stainless steel with silicone coating inside
Cuvette sealing:Viton O-ring
Internal tubing:FKM / Viton (fluorinated rubber)
Casing:High-quality table-top casing, aluminium
Dimensions (W x H x L):300 x 100 x 81 mm
Weight: approx. 1670 g
Gas connections:PVDF screw-type tube connection for tube Øi 4 mm, Øo 6 mm
Measurement data
Linearity error: < ± 1% F.S.
Repeatability: ± 0.5% F.S.
Long term stability zero: < ± 1% F.S. / 24 h
Long term stability span: < ± 1% F.S. / month
Temperature influence of zero point: < 1% F.S. / 10K
Temperature influence of span: < 2% F.S. / 10K
Cross sensitivity: < 2% F.S.
Pressure influence: < 1.5% / 10 hPa of reading
Warm-up time: 1 min (initial), < 15 min for full specification
Response time (t90): 1.5 – 15 sec
Sampling frequency by software: ≤ 10 Hz
Detection limit: See Table of Measurement Ranges
Resolution: 0.5 x detection limit
Electrical features
Power supply:  24 VDC incl. power plug 100 ~ 240 VAC
50/60 Hz: 24 VDC
Supply current (peak): < 0.4 A
Average power consumption: < 7.5 W
Interface: USB (standard)
RS232 / CANbus / CANopen (options)
incl. data transmission cable 1 m
Analogue voltage output (option):  0-2 V / 0-5 V / 0-10 V
Gas parameters
Operating temperature: +5 ~ +45 °C
Storage temperature: –20 ~ +60 °C
Operating pressure: 800 ~ 1200 hPa (mbar)
Ambient humidity:0 ~ 95% rel. humidity
Condensing inside of sensor must be prevented!

List of standard measurement ranges *1 ( and detection limits *2 )

Standard Measuring Ranges with respective Detection Limits ( % of F.S. *3 )
100
Vol.%
50
Vol.%
30
Vol.%
20
Vol.%
10
Vol.%
5
Vol.%
1
Vol.%
5,000
ppm
2,000
ppm
1,000
ppm
500
ppm
300
ppm
100
ppm
50
ppm
10
ppm
1
ppm
SO2
(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.5%)

(< 0.5%)

(< 0.5%)
H2S
(< 0.1%)

(< 0.1%)

(< 0.1%)

(< 0.2%)

(< 0.5%)
*1 A standard measurement range is defined by / *2  (= 3 σ) in Percent of Full Scale / *3 F.S. = Full Scale / *4 Calibration with Propane

Infrared module NDIR Ultraviolet module NDUV

Definition of Detection Limit

The Detection Limit is the smallest measurement value which can be obtained with a specific uncertainty. This uncertainty includes the resolution, noise and stability of the gas sensor for a specific gas and specific measurement range. For evaluation of the detection limit value, several single measurements are taken at the identical measurement conditions. With the obtained single measurement results the standard deviation “Sigma” (σ) is calculated. The values given in the table equal the triple amount of Sigma.

Recalibrations

The following recalibration intervals are recommended for UV sensors:

  • Zero-point:
    • Concentrations < 300 ppm: Every 48 hours with inert gas, e.g. Nitrogen
    • Concentrations ≥ 300 ppm: Every 24 hours with inert gas, e.g. Nitrogen
      The recalibration of the zero point is described in the software manual.
  • End-point (full scale): Every 3 months with suitable calibration gas

V 1.0 / Rev. 2024-02-07 / Subject to alterations.