btl Archives - AUTOMATION INSIGHTS

Quick field replacement for linear sensor electronics

Micropulse Transducers BTL 7 Rod-style with Rapid Replacement Module — Micropulse Transducers BTL 7
Rod-style with Rapid Replacement Module

When maintenance technicians replace linear position sensors (also known as probes or wands) from hydraulic cylinders, it can leave a terrible mess, waste hydraulic oils, and expose the individual to harmful hot fluids. Also, the change out process can expose the hydraulic system to unwanted contaminants. After the sensor replacement has been completed, there can also be more work yet to do during the outage such as replacing fluids and air-bleeding cylinders.

Hydraulic linear position sensors with field-replaceable electronics/sensing elements eliminate these concerns. Such sensors, so-called Rapid Replacement Module (RRM) sensors, allow the “guts” of the sensor to be replaced, while the stainless steel pressure tube remains in the cylinder. The hydraulic seal is never compromised. That means that during the replacement process there is no danger of oil spillage and no need for environmental containment procedures. There is also no need to bleed air from the hydraulic system and no danger of dirt or wood debris entering the open hydraulic port. Finally, there is no danger of repair personnel getting burned by hot oil.

The RRM is an option for Balluff’s BTL7 Z/B Rod Series used in applications for the lumber industry, plastic injection and blow molding, tire and rubber manufacturing, stamping presses, die casting, and all types of automated machinery where a continuous, absolute position signal is required. Applications in industries such as Oil & Gas and Process Control are especially critical when it comes to downtime. For these applications, this Rapid Replacement Module capability is especially advantageous.

You can learn more about linear position sensors with hazardous area approvals, by visting http://www.balluff.com/local/us/products/sensors/magnetostrictive-linear-position-sensors/

The video below shows a demonstration of the Rapid Replacement Module in action.

Hydraulic Cylinder Position Feedback, Revisited

In a previous Sensortech post entitled “Hydraulic Cylinder Position Feedback“, we discussed the basic concept of hydraulic cylinder position feedback. In case you might have missed that post, here it is for an encore appearance.

Magnetostrictive linear position transducers are commonly used in conjunction with hydraulic cylinders to provide continuous, absolute position feedback. Non-contact magnetostrictive technology assures dependable, trouble-free operation. The brief video below illustrates how magnetostrictive position sensors are used with hydraulic cylinders.

Continue reading “Hydraulic Cylinder Position Feedback, Revisited”

Thinking Outside the Cylinder

In a previous entry, I discussed how linear position sensors are used with hydraulic cylinders to provide continuous position feedback. While this is certainly one of the most common ways linear position sensors are used, there are many applications for linear position sensors that either don’t involve a hydraulic cylinder at all, or that involve a cylinder only indirectly.

Linear position sensors for external use (not installed into a hydraulic cylinder) offer some very tangible benefits when compared to in-cylinder sensors. Let’s explore a few of those benefits:

Continue reading “Thinking Outside the Cylinder”

Hydraulic Cylinder Position Feedback

Today, we’re going back to basics with one of the most common applications for linear position sensors: hydraulic cylinder position feedback.

Continue reading “Hydraulic Cylinder Position Feedback”

Analog Signals: 0 to 10V vs. 4 to 20 mA

In the world of linear position sensors, analog reigns supreme. Sure there are all kinds of other sensor interface types available: digital start/stop, synchronous serial interface, various flavors of fieldbus, and so on. But linear position sensors with analog outputs still account for probably two-thirds of all linear position sensors sold.

When choosing an analog-output position sensor, your choice generally comes down to analog voltage (e.g., 0…10 V), or analog current (e.g., 4…20 mA). So which should you choose?

0…10V versus 4…20 mA

When it comes to sensor interface signals, 0…10V is like vanilla ice creamr. It’s nothing fancy, but it gets the job done. It’s common, it’s straightforward, it’s easy to troubleshoot, and nearly every industrial controller on the planet will accept a 0…10V sensor signal. However, there are some downsides. All analog signals are susceptible to electrical interference, and a 0…10V signal is certainly no exception. Devices such as motors, relays, and “noisy” power supplies can induce voltages onto signal lines that can degrade the 0…10V sensor signal. Also, a 0…10V signal is susceptible to voltage drops caused by wire resistance, especially over long cable runs.

A 4…20 mA signal, on the other hand, offers increased immunity to both electrical interference and signal loss over long cable runs. And most newer industrial controllers will accept current signals. As an added bonus, a 4…20 mA signal provides inherent error condition detection since the signal, even at its lowest value, is still active. Even at the extreme low end, or “zero” position, the sensor is still providing a 4 mA signal. If the value ever goes to 0 mA, something is wrong. The same can not be said for a 0…10V sensor. Zero volts could mean zero position, or it could mean that your sensor has ceased to function.

In some cases, 4…20 mA sensors can be slightly more costly compared to 0…10V sensors. But the cost difference is becoming smaller as more sensor types incorporate current-output capability.

For more information on linear position sensors, click here.