Page last updated: 7th September, 2020
INT Series Digital Panel Meter FAQs
The once humble digital panel meter has evolved greatly over the past few years.
They can perform many more useful functions which used to be possible only with PLCs or specialist equipment. This makes them a cost effective and easy to use alternative to PLC systems.
Their most basic function is as an indicator. They can accept most industrial sensors and signals and can be scaled to read in engineering units.
Here are a few common questons we are asked...
* I have a serial number, how old is my meter?
* What are 3 1/2 and 4 1/2 digital panel meters?
* How are digital panel meters scaled?
* What is analogue output used for?
* What are alarm relay outputs used for?
* What are data outputs used for?
* What are logic inputs used for?
* Are these digital panel meters customisable?
* What power voltages do these digital panel meters use?
* What digit sizes are available on these digital panel meters?
* What digit brightnesses are available on these digital panel meters?
* What digit colours are available on these digital panel meters?
* What environmental sealing is available on these digital panel meters?
* What is sensor excitation?
Our INT series of digital panel meters has a high-stability averaged 20 bit A/Dfor excellent resolution, precision and repeatability. It provides 6 digits, and you can choose to use only 1, or 2,3,4,5 or all 6 digits, dpending on your application.
The displays have leading zero blanking, which means that for a small number, like 123, we display 123 instead of 000123, which improves clarity and speed of understanding of the value.
The ultimate in modular flexiblity
Our digital panel meters and displays use a common architecture, shown below. You can use as few of the options or as many as you like, this level of flexibility, coupled with high resolution and precision makes these instruments particularly valuable to distributors and process engineers, as you can be sure a combination will be available to fulfil your needs.
Q. I have a serial number, how old is my meter?
You can find when your meter or large display was manufactured with our online lookup tool.
This is available at https://www.london-electronics.com/whenmade_new.php
Q. What is meant by the 1/2 digit in a 3 1/2 digit, 4 1/2 digit or 5 1/2 digit panel meter?
You've probably heard the terms 3 1/2 digit, 4 1/2 digit and 5 1/2 digit panel meter, and wondered what they mean. After all, how can you have half a digit?
Look at the digital readouts below...
The 3 1/2 digit display can be used to show values from -1999 to 1999, and can include a decimal point, by lighting up the red segments, to suit the number you want.
If you count the number of segment connections to each digit, you'll see that the 1st digit has only 4 wires, because there are only 4 segments.
The other digits have 8 wires (Although we often refer to these as '7 segment' displays, if you include the decimal point, there are really 8 segments)
We say that the left hand digit is only half a digit, as it has half the number of segment connections of a full digit.
3 digit display...
3 1/2 digit display...
4 digit display...
4 1/2 digit display...
5 digit display...
5 1/2 digit display...
6 digit display...
The INT series of digital panel meters and Fusion series of large digital displays can be used in any application calling for a 1 digit, 1 1/2 digit, 2 digit, 2 1/2 digit, 3 digit, 3 1/2 digit, 4 digit, 4 1/2 digit, 5 digit, 5 1/2 digit or 6 digit readout.
Scaling of digital panel meters
The scaling of the panel meter is uniquely simple in the INT4 and Fusion series, allowing you to perform sensor scaling in a matter of seconds. No complex menu programming is used - a real benefit, saving you time and reducing stress. For non-linear systems, we offer 10 point user adjustable linearisation, which is ideal, for example, when using pressure transmitters to monitor tank volume in curved-sided tanks.
They can even give a mirror image display value to allow you to use the panel meters in heads-up applications.
We make life easy for you by using detachable screw terminals.
From your displayed value, we can generate various outputs which we describe below. You can use these for control, recording or system expansion:-
1. Analogue output
Analogue outputs are normally used to send the digital panel meter's measured value to another device, such as a PLC, datalogger, chart recorder or remote display.
This is generally safer than sharing the sensor's input signal with several devices, as there is less chance that the signal will be corrupted by noise, cabling or connection faults, or by changes in load impedance.
We use a high precision 16 bit D/A system, which ensures that the precision and resolution of the analogue output is high.
We also electrically isolate the analogue output signal from the rest of our circuitry, so that you can confidently connect it to any other equipment without creating a ground loop.
The analogue output can easily be scaled to suit your measurement range. We offer different outputs to suit most requirements, such as 4-20mA, 0-10V and -10 to +10V.
The analogue output can be scaled in proportion to your measurement or in inverse. For example, 0-25000 kg = 4-20mA or 25000 to 0 kg = 4-20mA. It can also be derived from the nett or gross value of your display.
For a full description on the capabilities of the analogue outputs in the INT4 series, please see [here].
2. Alarm Relay outputs
It is often useful to compare your measurement to a reference value and create an output if your measurement goes above or below the reference value.
For example, you may wish to control the level in a storage tank, so that once the level drops to a minimum acceptable level, a relay switches on a pump to refill the tank to a maximum chosen level. This technique reduces the burden on the pump and switchgear as the level is allowed to vary in a band, rather than trying to maintain a fixed volume.
Another common application for the alarm relay outputs is to control the amount of product being filled into bags, boxes, hoppers or vehicles. The alarm relay shuts off the feed once the required amount has been loaded. A refinement to this system is known as 'in-flight compensation'. This shuts the relay shortly before the final weight is achieved, because there will be some material still 'in-flight' which will add to the final weight once it lands. The INT4 series of panel meters can automatically adjust the amount of in-flight compensation to allow for variations in material flow characteristics caused by changes in moisture content, particle size etc.
Relays can also have fully adjustable hysteresis to prevent relay chatter and can be set to be normally de-energised or normally energised, for creating failsafe alarm systems.
We use high quality gold-plated relay contacts to give you the very best reliability in your system.
You can compare your alarm setpoints with the gross or nett value of your measurement, useful in many batching applications.
Our alarm relay outputs are also available as solid state devices, if that suits your application better. In addition, we include timers to allow you to delay the activation of an alarm relay unless the alrm condition has been present for a certain amount of time. Similarly you can delay the reset of the alarm unless the condition has been clear for a preset amount of time.
For a full description on the capabilities of the alarm relays in the INT4 series, please see [here].
3. Data outputs
Often, devices need to share their measurement with serial data networks. We offer a number of useful output types to provide point to point or addressed data sharing.
A useful application allows the connecting of several digital panel meter comms ports together, to be interrogated by a simple service application wheich we can write for you, which posts the values periodically to a cloud-based database. You can then access near-live data from any browser connected to the internet over https or TLS secure link, with one-way encrypted password access. You can view historic data, trends, alarms, graphs etc.
For a full description on the capabilities of the data output in the INT4 and Fusion series, please see [here].
4. Logic input ports
Our digital panel meters have several logic input ports which you can use to trigger certain actions. For example you can programme a logic input to Tare your display. Or to reset it. Or to freeze the display. Or to blank it. Or to show the peak or valley value. Or to show a 2nd scaled value for metric/imperial applications. Or to toggle between net and gross. Or to trigger a print output data transmission.
5. Customised features
Our digital panel meters are used in so many diverse applications, we invite users to request their own custom special functions. The architecture of the displays is such that it is reasonably straightforward for us to edit the code to provide unique features specific to your needs. If you don't see a feature you would like - just ask!
6. Power supply voltage
Most of our digital panel meters are used in systems where 95-265V AC or 11-30V DC is available. We also offer 48V AC in the Fusion series of large displays, often required in crane systems.
7. Digit height
We have the widest range of digit heights for our displays. Our traditional digital panel meters have digits 14mm high, suitable for viewing up to 7m away, but the full range of digit sizes we offer is ...
8. Digit brightness
We offer displays for use inside and for use outside in direct sunlight. All displays have several levels of selectable brightness to allow you to reach the best level as brightness changes throughout the day..
9. Display Colour
The most popular display colour is red, but we can offer many other colours including amber, green, blue and white. Our new INT5 series panel meter range has red, amber and green available as standard.
Our standard panel meters are sealed to IP65 but we have the option of raising this to IP67. Our large displays are designed to be permanently mounted outdoors, we have numerous examples of displays which have been running 24 hours a day for 20 years outside in all weathers - that is reliability!
11. Sensor Excitation
Sensor excitation is an output voltage provided by the digital panel meter or large display to power your sensor.
We provide a power supply output on most of our digital panel meters for this purpose. For load cells, we provide 10V DC at up to 120mA, which is sufficient to power 4 x 350 Ohm cells. For process meters, we provide 24V DC to power 4-20mA loops, and can also give 10V DC to power 3-wire potentiometers.
Any questions? Just ask, we are here to help!