Instrumentation
Selecting the right dewpoint sensor and transmitter type to meet the stringent needs of your unique installation is a critical task. Steven Jiroutek guides you through the most essential questions you should answer when weighing your choices.
Die Auswahl des richtigen Taupunkt-Sensors und Taupunkt- Transmitters ist eine kritische Aufgabe, um den strengen Erfordernissen Ihrer spezifischen Anlage gerecht zu werden. Steven Jiroutek führt Sie durch die wichtigsten Fragen, die Sie vor Ihren Entscheidungen beantworten sollten.
Le choix du capteur de point de rosée et le type de transmetteur qui conviennent pour répondre aux impératifs sévères de votre installation personnalisée est une tâche cruciale. Steven Jiroutek vous guide parmi les questions les plus essentielles auxquelles vous devrez répondre lorsque vous faites votre choix.
Find the right dewpoint meter for compressed air application
T
Fig. 1. Spot-checking is easy with a lightweight hand-held meter such as the DM70.
he first question to ask is whether you are you looking for a fixed or a portable dewpoint sensor and
transmitter.Fixed mount transmitters usually require an external power
source to operate and can range in complexity from a basic analogue only device to very sophisticated units with displays, alarm relays, datalogging, ethernet connections, and more. The following set of questions will help narrow
down products to choose from. What do you need the instrument to do?
n Continuously monitor with a local display? n Panel meter or integrated display? n Send a signal somewhere for control or other purposes? What type of signal?
n Alarm at a high/low setpoint? n Datalog?
Fixed mount units can be installed on supply- side OEM applications, for dryer monitoring or control, as well as on the demand-side for end user applications connecting to PLCs, dataloggers, and panel meter displays. In terms of portable handheld devices, these
battery-powered mobile devices of varying size and function are optimised for different applications.
They are typically used for verifying fixed mount transmitters in the field or for spot-checking various points in a compressed air system (Fig. 1).
Dryer type In most compressed air systems, the type of dryer will dictate the dewpoint operating range required from the dewpoint instrument or sensor type. Currently there is no single instrument on the
market that measures all dewpoint levels well. Sensing technologies are optimised to excel in specific ranges – very dry conditions, mid-range ambient levels, or high humidity condensing environments. Measuring dewpoint in each of these ranges presents its own unique set of challenges (Fig. 2).
Choosing the instrument with the right
measurement range will impact both the short- and long-term accuracy and stability of the dewpoint measurement.
Desiccant dryers Compressed air systems using a desiccant-type dryer can have dewpoints anywhere between -100 and -30°C (-148 2 to 22°F). However, most operate between -60 and -40°C (-76 to -40°F). It’s important to identify what level you actually wish to control or monitor. If your dryer outputs air at -80°C
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