The Basics of Level Measurement

The level of a liquid or solid inside a container can be defined as a distance between the top surface of the material and a reference point.

We have a surprising range of sensor technologies to determine just how much material is in a container. Here is a list of some of the measurement methods and a brief description of these technologies.

  • Capacitive
  • Differential Pressure
  • Floats
  • Lasers
  • Magnetic
  • Radar
  • Ultrasonic
  • Vibration

Capacitive

Changes in the electrical properties of the space between two electrodes on a switch or between a long probe and the container itself indicate changes in level. These devices include both continuous gauges and point level switches.

Differential Pressure

These measure level based on the pressure difference between the bottom of the container and the head space (for pressurized vessels) or atmospheric pressure for vented containers.

Floats

A mechanical float moves with changing level and a complementary detection technology is used to determine the position of the float displacers. The apparent weight of the displacer varies with level.

Lasers

Laser level devices are top mounted, non contact devices that project a laser beam toward the surface. Time of the flight is used to calculate distance of the material level from the top of the container.

Laser have developed an application niche, especially in the measurement of bulk solids and powders.

Magnetic

These are the variation on the float level devices. A float containing a permanent magnet moves freely up and down.

Radar

These uses a beam reflected radar signal to determine level. Radar is relatively expensive in the more accurate versions.

The radar technology have been increased in recent years. This growth has been driven by high speed processing chips and falling sensor prices as more suppliers make pulse radar components for sensing devices in cars.

Ultrasonic

These operate similarly to radar devices, but calculate level based on the time required for an ultrasonic signal to be reflected from the liquid surface. The sensor emits a high frequency pulse, generally in the 20 kHz to 200 kHz range and then listens for the echo.

Ultrasonic level measurements is the most widely used non contact technology. Ultrasonic level transmitters are used in most industries and are very widely used in open channel flow measurement systems.

Vibration

These detect the presence of liquids or solids based on the shift in resonant frequency of a vibrating probe.

Related Material and Technologies

NameDescription
KROHNE KROHNE is a manufacturer and supplier of solutions in industrial process instrumentation.
VEGAVEGA is a global manufacturer of sensors for measuring level, point level, pressure as well as devices and software for integrating them into process control systems.
Massa Massa manufactures sonar and ultrasonic products for use in the water and air.
NewarkNewark is a distributor of technology products, services and solutions for electronic system design, maintenance and repair.

Related Services

If you are interested in our services related to automation or instrumentation and control please feel free to contact MultiSequence at info@multisequence.com or +1 (844) 800-MSEQ

How to Enable X11 Forwarding on Amazon Linux

X11 Forwarding can be configured on Amazon Linux instance created from AMI version 2017.09.01 with following steps. These may work with recent version of Amazon Machine Images (AMIs).

Step 1: Verify or install  required X11 packages

List installed X11 packages with following command.

$ sudo yum list installed '*X11*'

Installed Packages
libX11.x86_64
libX11-common.x86_64
xorg-x11-font-utils.x86_64
xorg-x11-fonts-Type1.noarch

It would be required to install package xorg-x11-xauth.x86_64 which can be installed with following command.

$ sudo yum install xorg-x11-xauth.x86_64 -y

Once installed exit and reconnect SSH session. You may notice following information upon reconnecting.

/usr/bin/xauth: creating new authority file /home/ec2-user/.Xauthority

Display can now be forwarded to an X11 Client from Amazon Linux.

Additional step are for configuring PuTTY with Xming client on Windows.

Step 2: Install Xming Client for Windows

Install Xming program for Windows that can be downloaded from Xming Site or searching on the internet.

Once installed, make sure server is started after the installation that can normally be seen in Taskbar notification area as Xming Server:0.0

Xming display settings are configured as following.

xming

Step 3: Configure PuTTY to enable X11 forwarding

PuTTY can be utilized to connect to Amazon Linux from Windows environment. PuTTY’s SSH session can be configured to enable X11 forwarding as shown in the following image.

putty-x11-forwarding

Now once connected to the Amazon Linux instance utilizing SSH protocol through PuTTY, display would be forwarded to the local Windows machine.

How to Upgrade Java on Amazon Linux

Java version on Amazon Linux instance created from AMI version 2017.09.01 can be upgraded with following steps. These may work with recent version of Amazon Machine Images (AMIs).

Step 1: Copy the required version of Java to Amazon Linux

For this exercise we would be upgrading to Oracle Java 8 update 121 utilizing package jdk-8u121-linux-x64.rpm which can be downloaded from Oracle Downloads.

Once downloaded this can be copied to the Amazon Linux instance with Secure Copy Protocol (SCP).

Step 2: Remove currently installed Java version

List current Java version information with following command.

$ java -version
java version "1.7.0_161"
OpenJDK Runtime Environment (amzn-2.6.12.0.75.amzn1-x86_64 u161-b00)
OpenJDK 64-Bit Server VM (build 24.161-b00, mixed mode)

List currently installed Java package.

$ sudo yum list installed '*java*'

Remove currently installed Java package.

$ sudo yum remove java-1.7.0-openjdk.x86_64 -y

Verify Java is uninstalled.

$ java -version
-bash: /usr/bin/java: No such file or directory

Step 2: Install newer version of Java

Navigate to the location where newer version of Java was copied.

$ pwd
/home/ec2-user
$ ls
jdk-8u121-linux-x64.rpm

Run following command to install Java.

$ sudo rpm -ivh jdk-8u121-linux-x64.rpm

Verify that Java is successfully installed.

$ java -version
java version "1.8.0_121"
Java(TM) SE Runtime Environment (build 1.8.0_121-b13)
Java HotSpot(TM) 64-Bit Server VM (build 25.121-b13, mixed mode)

$ echo $JAVA_HOME
/usr/lib/jvm/jre

$ which java
/usr/bin/java