Programmable Timers
The Many Types of Programmable Timers
The Programmable Timer is used for measurement, display and control in applications that have variables. A Programmable Timer can also work with a single input or, in some cases, a pair of signals. Timers exist because many processes are based upon timed events. Programmable timers are usually electronic and use digital displays, precise digital set-ability, high accuracy, and fast reset times. Digital electronic timers use LCD or LED displays and offer long time ranges and come in a several types.
Preset Counters
When specifying this specific type of programmable timer, consider the following:
- Input - what will be counted and where will the input be obtained
- Count Speed
- Number of digits - based on maximum count value
- Type and Size of Display
- Packaging - requirements and enclosure size
- Environment
Rate Indicators and Controllers
The second group of Programmable Timers includes rate indicator and controller. Rate indicators
provide a digital display of a process. Simple versions connect to a sensor and give a direct readout of frequency or voltage, which represents rate or speed. Units can show variable such as motor revolutions per minute or material feet per minute. Some rate meters have calibration that scales, or converts, the input signal to engineering units using a sensor. Rate controllers add the ability to compare input to one or more values or "alarms". These "alarm" can trigger control outputs or relays to prevent out-of-tolerance operation or take corrective action to bring the process within normal limits. Some programmable rate metering products can measure process times. This is a measurement made of how long a process takes, rather than how fast it is going. They may be used on conveyor lines to indicate the time a
product spends in a galvanizing tank or baking oven.
Additional considerations when specifying this particular type of programmable timer, include:
- Ambient Light
- Warning Light/Alarm Requirements
- Additional Power Supply for Sensing Devices/Alarms
- Communication Links
Time Indicators and Preset Timers
Time Indicators, like the Veeder Root
7795 Series above,can be found with many
different timing ranges, depending on the application
in which it is needed.
When specifying these programmable timers for your application, consider:
- Control Function - reset, repeat cycle
- Time Range
- Mounting Types
- Size
- Service Voltage and Frequency
- Setting Accuracy
- Repeat Accuracy
- Front Panel
- Load - What device will be controlled by the timer and specs
- Cycle Rate
- Action on Power Failure
- Operator Restraints
- Special Requirements - NEMA, high temp/humidity, corrosive, electrical interference
- Agency Approval
Multifunction Indicators/Controllers
The final type of Programmable Timer is the multifunction indicator/controllers. The multifunction instruments are combinations of totalizers, predetermining counter, and rate measurement techniques. They do the job of several instruments, saving time, money and panel space. These devices are used when applications require multi-step, sequential operations by count and/or time. One example is for this device is for liquid transfer and dispensing operations - providing totals and rate functions. The counters described need a signal that represents the unit to be counted, which is often available as a voltage pulse or contact closure. When no signal is available, a sensor
will be needed.
Programmable Timers are available in ranges as large as 0.01-9999 hours and as precise as 0.05-5 seconds. Choose from a variety of cycle types, delays times and special considerations such as NEMA ratings.
Programmable Timer Video Overview