For decades, process instrumentation has largely relied on 4-20 mA signals to transmit process data easily and reliably. Moreover, it is the signal of choice in the process control industry for many reasons. One in particular is the fact that current does not degrade and it remains constant at any point in the loop, as discussed in our review of the Fundamentals of 4-20 mA Current Loops. Therefore, it is a very efficient means to transmit process information. In most cases, this range represents a two-point linear scale where a 4 mA signal represents 0% of a sensor's measurement, while 20 mA indicates 100% of the measurement. But, why do we use 4-20 mA instead of 0-20 mA? That is a very common question among individuals in the industry. And the answer is simple; a 0 mA signal is not practical. This article will discuss three reasons why a 0 mA signal is not as useful and why 4-20 mA is the industry standard.
Precision Digital now provides some cool new tools for working with 4-20 mA and other common signals that are handy to have in your toolbox or on your work bench. The PD9502 is a simple-to-use 4-20 mA or 0-10 VDC signal generator with a 4-digit LED display and a one-turn adjustment knob. The PD9502 can be powered by 15-27 VDC or optional USB power bank. The PD420 panel mount set point generator provides a convenient way to generate a 4-20 mA signal that can be used to control another device and features a built-in dial for coarse or fine adjustment. The PD9501 multi-function calibrator has a variety of signal measurement and output functions including voltage, current, thermocouple, and RTD. The PD9501 also includes a convenient storage case and 3 easy connector cables. Learn more about these must-have tools in this webinar presented by Joe Ryan, VP of Sales and Marketing.
What You Will Learn:
- How these products can simplify your life and save you money.
- Actual demonstration of PD420 Set Point Generator and PD9502 Signal Generator in action
- All in a quick 20-30 minute presentation
Precision Digital has released variety of new and exciting products, so it’s time to check-in on the What’s New section at predig.com/whatsnew. Here, you will learn about our wide range of Light/Horn options and modifications for the ProVu and Helios meters, and various enclosures. The light/horn is available in a variety of colors and the light and horn can be controlled independently of each other via separate relays. The light can be programmed to flash or stay steady on. We have some cool new tools available for generating and controlling 4-20 mA and voltage signals for your process instrument. These include a low-cost signal generator, 4-20 mA set point generator and a multi-function calibrator. You will also see our new PDA6405 accessory. This line of split-core AC current transformers is ideal for converting the high current flowing through a cable or wire to a 0-5 A output. Another useful accessory for converting current is our PDA6420 split-core current transducer. The PDA6420 can convert the current flowing through a cable wire to a 4-20mA signal.
Precision Digital recently conducted a webinar on the New Light / Horn option for ProVu and Helios process meters. Learn how Precision Digital’s new Light / Horn Option adds visual and audible alarm capabilities to our meters. If you missed the webinar or want to see it again, you can visit predig.com/webinars and watch the previously recorded webinar. We also provided the slide presentation as a PDF download.
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This video will introduce Precision Digital's new Light and Horn option for the ProVu and Helios process meters. The light and horn option includes a flashing red light that can be set for flashing or stay steady on, a horn that is rated at 85 dB, and a reset button. The light and horn can be controlled separately by relays. Watch this video that includes demos of both the ProVu and the Helios meters with the Light / Horn option.
- Measuring AC Current with the PDA6405 Transformer