• HT8700 Open-path NH3 Analyzer

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HT8700 Open-path NH3 Analyzer
Advanced QC laser spectroscopy for atmospheric ammonia analysis
HT8700 is an open-path analyzer providing in-situ measurement of atmospheric ammonia (NH3 ) concentrations with high speed, low power consumption, and ultra-high sensitivity.The superior performances make it suitable for on-site deployment in various environments,including urban, rural, remote fields, and even mobile monitoring platforms.
Revolutionary Open-path Design for Ammonia
NH3 gas has strong adsorption and viscosity.Conventional closed-path analyzers often suffer great analytical errors due to sample adsorption to the inner surface of the sampling tube.HT8700 has the open-path design that avoids delays due to sample adsorption. The signal response time can be as short as 0.1 second.
Note:Although open-path analyzers have low availability of data under high humidity or rainfall,NH3 concentration is very low in these cases due to its high adsorption and high solubility. Hence,the error of the overall flux measurement is little.
Mid-infrared Laser Spectroscopy
HT8700 is based on the state-of-the-art Quantum Cascade Laser Absorption Spectroscopy (QCLAS) technology, which utilizes the strong absorption line of NH3 in the mid-infrared spectral band. Multiple reflections of the laser beam between two high-reflection mirrors create a long optical path that makes strong signals. The absorption energy at the spectral line is extracted and the gas concentration is retrieved with sub-ppbv sensitivity. There is no overlap of absorption peaks with H2O,CO2,and other atmospheric trace gases,which realizes the anti-interference measurement.
Ammonia molecules have stronger absorption lines in the mid-infrared band
SPIDER®( Spin Dust Eliminate Rotor ) is a patented technology that utilizes an automatic rotating brush to remove the dust from the lower mirror, avoiding routine manual cleaning.
Strong mid-infrared absorber --> ultra-high (sub-ppbv) sensitivity
Distinct absorption lines --> high selectivity
No consumables and auto cleaning --> unattended continuous monitoring
Open-path --> fast response and no high frequency loss
No sampling pump and pretreatment --> low power and small footprint
Tested Accuracy
A test at the Shanghai Academy of Environmental Sciences compared the HT8700 with a closed-path analyzer from a leading brand.The concentration data from the two analyzers showed a high degree of consistency, confirming the accuracy of the HT8700.
Tested Speed
The field data showed no discernible delay of the NH3 measurements of the HT8700 compared to H2O measurements of the LICOR® LI-7500.The test ensured the short response time that is essential for the NH3 flux measurements.
Mobile Analysis
A real-time mobile analyzing system based on the HT8700 provides a complete solution for high-speed and accurate NH3 emission monitoring and tracing.

Eddy Covariance Flux Measurement
Below is an example of NH3 flux data from a 48-hour continuous measurement during the fallow season at a dry rice paddy in Ningbo, Zhejiang Province, China.The data was acquired with an Eddy covariance system based on the HT8700 and an anemometer. A peak of NH3 was observed after the application of ammonium bicarbonate in the morning of 2020/4/24.
Clear lag time between NH3 concentration and vertical wind velocity was observed,which varies between 0.4 s and 0.3 s,particularly following fertilizer application.
Spectral analysis was performed to study the instrumental performance in the high-frequency range.Note the CO2/H2O co-spectra were calculated based on the data from LICOR® LI-7500. Similarly, the NH3 co-spectra was calculated based on the HT8700 field data without high frequency loss correction.

Optical Path 0.5 m physical path;
46 m measurement path
Resolution( 1σ;0.1s/1s/10s) 0.3 ppbv/0.1 ppbv/0.03 ppbv
Measurement Range 0 - 2000 ppbv (other ranges are optional)
Output Data Rate 10 Hz/1 Hz/0.1 Hz
Operating Pressure 70-110 kPa
Operating Temperature -15 ~45 ℃
Operating Humidity 0~100% R.H. Non condensing
Data Communication RS-232
Power Requirements 20 - 28 VDC
Power Consumption Nominal 50 w( ~100 W at warming up)
Dimensions 834 mm x ∅200 mm
Weight <10 kg
Environmental Adaptability IP67
                                                                                                                   Ordering lnformation
ltem Part No. Note
open-path NH3
analyzer (1Hz)
For ambient NH3 concentration measurement .
The maximum update rate is 1 Hz.
open-path NH3
analyzer (1 0Hz)
For ambient NH3 concentration and eddy-covariance flux measurement .The maximum update rate is 10 Hz.
 instrument case
HT-8700-001 A precision instrument box for safe, shock-proof storage and transportation of HT-8700 analyzer, cables,and mounting accessories.
Circulating water
cooling system
An external heat dissipation device with circulating water ( or high-efficient antifreeze coolant) tubings used to remove the heat generated from HT-8700(E) .
Transportable cooling system case HT-8700-003
A precision instrument box for safe, shock-proof storage and transportation of the cooling system and water tubings.
SPIDER HT-8700-004 Automatic Spin Dust Eliminate Rotor to avoid manual mirror cleaning.
Mounting kit HT-8700-005 Structural fixture for fixing HT-8700 (E)on observation platform or carrier.
Power adapter and cables HT-8700-006 220VAC (110VAC ) to 24VDC power adapter and cables