Dynamic Voltage vs. 4-20 mA Proximity Probes Explained

A standard dynamic voltage system provides a voltage signal which is composed of detailed data for complex analysis and condition monitoring. While this is fantastic for those who have the correct equipment to analyze this data, not everyone has the training or hardware to perform complex analysis.

CTC's PRO Line 4-20 mA current drivers are great, low-cost solutions for applications where it is important to monitor the condition of the machine, but there is no budget or need for a full DAQ rack or MPS (Machine Protection System). 4-20 mA signals are very common process control signals utilized by PLC, DCS, and Control Room Monitors. 4-20 mA signals are very popular because they can travel long distances without degrading, and provide a constant reading that is very easily and cheaply read by a wide variety of commonly utilized equipment. All PRO Line 4-20 mA Drivers also feature a fully-isolated BNC on the front of the case, which provides the analyst access to the unfiltered voltage output of the probe.

The two main functions of a proximity probe system are to identify the vibration and position of a shaft relative to its housing. In order to provide monitoring solutions for these two metrics, CTC offers different 4-20 mA current driver types:

4-20 mA Radial Driver Series
This series of drivers focus only on the severity of the radial vibration occurring in the shaft measured as the distance between the negative and positive peaks of the vibration sine wave that is generated, also known as peak-to-peak (Pk-Pk) measurements. This is accomplished by only focusing on the AC portion of the original dynamic voltage signal and converting it into a 4-20 mA process signal.

As vibration severity increases, the amplitude of the AC sine wave indicating vibration will increase, thus increasing the distance between the positive and negative peaks in the sine wave. This increase in distance between the peak-to-peak value is represented by an increase in the 4-20 mA output of the probe driver. So, as vibration grows more severe, the AC sine wave portion of the voltage signal will grow larger, which increases the peak-to-peak value and is represented by an increasing 4-20 mA signal. The scaling of this 4-20 mA signal is configurable when ordering this driver type. Below is an example of what peak-to-peak measurement of a waveform looks like:

4-20 mA Axial Probe Driver Series
This series of drivers only focuses on the DC portion of the original voltage signal and will provide the user data on the position of the shaft while filtering out the AC portion of the signal which indicates vibration. These are primarily used at the end of the shaft or on a shaft collar if there is one available to measure thermal expansion or axial thrust. Often this information is used to trigger alarms and switches to shut down a machine if the shaft moves beyond a designated distance from its original position.

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CTC is the world leader in the design and manufacture of industrial accelerometers and piezo velocity transducers, 4-20 mA vibration sensors, and proximity probe sets, as well as all related mounting hardware, cables and connectors, and junction boxes. Our products enable efficient vibration monitoring for predictive maintenance in a wide variety of industries. Industries served include cement, mining, petrochemical, food & beverage, auto, steel, wind, paper & pulp, power generation, water & wastewater treatment, pharmaceutical, hospitals, bottling, and more. Our mission is to offer the widest variety of accelerometers and vibration hardware products, which are compatible with data collectors and online monitoring systems, as well as the tools for installation.

The CTC product line features vibration analysis hardware for heavy industry. All CTC products are backed by our unconditional, lifetime warranty. If any CTC product should ever fail, we will repair or replace it at no charge.

CTC’s PRO Line offers the world’s most durable and reliable Proximity Probe Sets including drivers, probes, extension cables, and driver enclosures for 24/7 protection of critical machinery in the most demanding industrial environments. CTC PRO Line Proximity Probe Sets are compatible with all major data collectors. PRO Line products are covered by our best-in-class lifetime warranty on material and workmanship.


The TMP Line features vibration analysis hardware for research and development. All TMP products are backed by a five-year warranty on materials & workmanship for standard sensors and a two-year warranty for all accessories, cables, connectors, and custom & private-labeled products.

CANCELLATION POLICY:
Stock, built-to-order, and private-label products qualify for free cancellation only if canceled within 24 hours of order entry. 

After 24 hours of order entry:

• Stock products will be subject to a 25% cancellation fee
• Built-to-order and private-label products will be subject to a 50% cancellation fee

Custom products are non-cancellable at any time after the order is placed.

If you wish to cancel an order, please reach out to your CTC sales representative. The timestamp of when your email requesting cancellation was received will be honored for whether or not your request meets the free cancellation window.

RETURN POLICY:
All stock products may be returned for a 25% restocking fee if returned in new and unused condition within 90 days of shipment.

Built-to-order and private-label products qualify for a 50% refund if returned in new and unused condition within 90 days of shipment.

Custom products are quoted and built specifically to the requirements of the customer, which may include completely custom product designs or private-labeled versions of standard products for OEM customers. Custom products ordered are non-cancellable, non-returnable, and non-refundable.

EXPEDITED PRODUCTS CANCELLATION & RETURN POLICY:
All expedited CTC orders are non-cancellable and non-returnable.