Delta OHM HD45 17A, Manual

Page: 2 / 72

- 2 -
1. INTRODUCTION
The instruments of the HD45 and HD46 series are transmitters, indicators and
regulators suitable for measuring and monitoring the following environmental
parameters, depending on the model:
• Relative humidity (RH)
• Ambient temperature (T)
• Carbon dioxide (CO
2
)
• Dewpoint Temperature (DP, computed value)
These instruments are designed for ambient air monitoring. Typical applications are
air quality analysis in crowded buildings (such as schools, hospitals, auditoriums,
work sites, refectories etc). This analysis allows to adjust air conditioning systems
(temperature and humidity) and ventilation (air changing/hour) in order to achieve a
double target: obtain a good air quality in compliance with the ASHRAE and IMC
directives in force and save energy.
RH (Relative Humidity) measurement is obtained by means of a capacitive sensor.
The sensor is temperature compensated to assure accurate and reliable
measurements with the time. In HD46 models, relative humidity and temperature
sensors with their calibration data are contained in an easy-to-replace module.
The temperature T is measured by means of a high-accuracy NTC sensor.
CO
2
(Carbon Dioxide) measurement is obtained by use of a special infrared sensor
(NDIR technology: Non-Dispersive Infrared Technology) that ensures long-lasting,
accurate and stable measures, thanks to the use of a double filter and a special
measurement technique. The presence of a protection membrane, through which
sampled air flows, protects the sensor from dust and atmospheric agents.
The instruments are factory calibrated and require no further adjustment by the
installer.
The instrument is wall-mounted and sensors are built-in.
0÷10V voltage or 4÷20mA current analog output versions are available, along
with PC-connectable versions via RS485 serial port with MODBUS-RTU protocol,
allowing connection with multiple transmitters on the same network.
Relay-equipped versions allow direct monitoring of measured ambient parameters
when user-custom thresholds are exceeded. Monitoring activation is shown by LED
indicators (in HD46…R models only). The relays operation is very versatile: they are
provided with an activation mode when threshold limits (lower/upper limit) are
exceeded, and in single or double threshold mode. Thresholds are user-configurable
over the whole range.
The LCD display option allows immediate viewing of all instrument-detected
measures.
The models HD45 BVR and HD45 BAR are distinguished by the ability to indicate an
immediate level of air quality, through turning on of the LED indicators associated
with graphic symbols.
All instrument functions can be set up in a quick and intuitive way through connection
to a PC.