Why Should Sensors Be Isolated

Connecting a physical sensor to a data acquisition system is a serious undertaking. When mounted in the real world of electromagnetic signals and repetitive or one time emissions, several things should be considered. These topics are covered in much greater detail in Dataforth application note AN116, Why Use Isolated Signal Conditioners.

Signal Conditioning and Alias Filters

In general, most SCM have built-in Low Pass (LP) filters as part of their design. In addition to the obvious benefits of such filtering, there is the very important subtle benefit. Namely, SCM with high quality multi-pole LP filters can be viewed inherently as having anti-alias filtering capabilities.

Low Pass Filter Rise Time vs Bandwidth

This app note captures much of the design considerations used to create industrial, instrument class signal conditioners. Although this application note is a little heavy on the math, page 6 presents a few illustrations showing the excellent results of such detailed engineering effort.

Strain Gage Signal Conditioners

This app note will use the bridge circuit to measure strain gages.

Why Isolate Analog Signals?

Application Note AN116 five very real, and very different reasons to isolate every one of your analog signals.

RTD Tutorial

In three pages, this newsletter provides nearly everything you'd ever want to know about resistance temperature detectors, or RTDs. From the physics of temperature effects on electron flow to mathematical models and equivalent circuit behaviors... you will be happy to learn that someone else considers all these details in signal conditioning design!

Six Sigma - What? Why? How?

Product variation and defects undercut customer loyalty as well as company profits. Six Sigma is a rigorous, disciplined, data-driven methodology that was developed to enhance product quality and company profitability by improving manufacturing and business processes.

Windmill Applications

This white paper recommends what I/O typically needs to be monitored and what controllers are best suited on a windmill in order to provide the safest and longest trouble-free operation. Moreover, due to the special environmental nature of the application, what signal conditioning hardware should be used to assure successful operation.

Configurable 5B module?

The world's first configurable "5B" is now here … Dataforth engineering has created the configurable SCM5B48-01 Accelerometer Module.

Shielding and Grounding

Protecting signal lines against electromagnetic interference is important if you want accurate, reliable, repeatable data. Although this may be a universally accepted statement, many overlook some of the sources of electromagnetic interference.

5B for Piezo-electric Accelerometers

Dataforth now has a new 5B modular signal conditioner designed specifically to interface to IEPE type accelerometers! The SCM5B48 signal conditioner provides DIP switches (yes, DIP switches in a potted 5B) for configuration

Hysteresis Specifications

Hysteresis specifications are often combined with other phenomena such as repeatability, reproducibility, linearity, and dead band as part of the overall product specifications. However, some elements in a data acquisition system, sensors as an example, may have a denominate individual hysteresis behavior that should be considered in determining a total system error budget.

Miniature electronics... 8B modules

Tiny microprocessor chips containing millions of MOS type (metal oxide silicon) “transistor” cells now permeate all aspects of our daily lives … Dataforth's 8B module has reduced earlier designs to 20% the size at a lower cost yet still provide "Instrument Class" performance.

A Question from Dataforth’s President

What’s next? As you use Dataforth’s products, and we manufacture hundreds of analog signal conditioners as well as data acquisition system solutions, I need to hear what you want next!

Unbalanced Voltages Increase Cost

The electric 3-phase induction motor is the work horse of industry and represents a significant portion of industry’s electrical utility cost … An often overlooked phenomenon is that unbalanced three phase voltages are responsible for adding significant additional operational motor costs.

Dataforth Test Reports

Fortunately, there are no mysteries or unexplained phenomena about Dataforth Signal Conditioning Module (SCM) products. Their published specifications and proven quality are facts of reality, which you can rely upon with certainty. To help to prove the point, you receive a test report with each Dataforth SCM.

Normal Mode Rejection, NMR

The operational amplifier (OP Amp) with differential inputs is an essential component in industrial signal conditioning modules, SCMs ... Perhaps one of the most important design benefits of operational amplifiers is their ability to process differential inputs.

Bridge Circuit Measurements

What are the differences among full bridge, half-bridge, quarter bridge circuits and voltage or current excitation of these Wheatstone bridge circuits? There's enough difference to present you with a six (6) page detailed application note!

Signal-to-Noise Ratio, SNR

The ratio of an information signal to the noise associated with observing this signal is a figure of merit that describes the quality of a communication system. Consider for example the Voyager 2 Space Craft ...

Accuracy versus Resolution

Many times distinguishing between accuracy and resolution is misinterpreted in determining system needs. Some examples and illustrations are presented in this Application Note.

Filtering - Phase Angles & Time Delays

This newsletter, with the link to App Note AN113 can be considered as Part 2 to App Note AN112 "Filtering in Signal Conditioning Modules". This one provides design considerations relative to phase angles and time delays.

Uncertainty Principle

Heisenberg’s "uncertainty principle" ... (does not apply) ... in Dataforth’s products, which have specifications that can be precisely measured and directly observed in use.

Galvanic Isolation

Using batteries is one technique for developing circuits that are isolated. Designing "Galvanic Isolation" into your products is just as effective. Dataforth's signal conditioners are designed with full 3-way isolation - the signal path, the field circuit power supply and the system circuit power supply are each isolated!

Signal Conditioner with Power Supply

Think about any hand-held multimeter and you will agree how important input protection and isolation are to most measurement applications! ...

Confident Strain-Gage Measurements

For load-cells, torque measurements, or for almost any bridge completion circuit, Dataforth probably has the "strain gage" signal conditioner you need! We have full, half and quarter bridge signal conditioners. Analog voltage or current output as well as RS-232 or RS-485 output conditioners ...

Signal conditioners - Buy vs Build

Sure I'm going to be somewhat biased! We design and manufacture signal conditioners so my arguments are going to be in favor of buying the devices and not building them! Okay! But the reasons to buy them are very good ...

Sampling Law

Analog data is stored by modern acquisition systems in digital form. Therefore, analog information must first be transformed to its digital equivalent using an analog-to-digital converter (ADC). In this type of system, the sample rate MUST exceed the highest frequency contained in the “detectable” input signal ...

Resistor Thermal Noise

Noise in measurement and control systems is generally considered to be EMI, electromagnetic interference. Unwanted voltages and currents induced by external magnetic fields, electric fields, ground currents, etc fall into the category of "noise" and often cause serious errors in low level instrumentation. ...

Filtering in Signal Conditioning Modules

Electrically and magnetically induced noise voltages or currents are inevitable. Field sensors with output voltages in the millivolt range are certainly degraded by induced noise levels on the order of volts. Consequently, signal conditioning modules must provide filtering to eliminate induced noise components ...

Filtering Noise

Signal conditioning modules, SCMs, used for measuring process control variables such as temperature, pressure, strain, position, speed, level, etc. are always subject to externally induced noise signals. Noise sources in the form of electro-magnetically induced voltages (or currents) in industrial measurement and control systems are inevitable ...

Power Supply Sensitivity

System engineers use signal conditioning module (SCM) transfer functions as ratios of module outputs to sensor inputs in terms of units applicable to their particular system applications. ... System error budgets should always be initially analyzed to ensure that the combined impact of changes in environmental conditions ... are within acceptable system error limits.

Measured vs Combinational Error

Astute system engineers must determine an acceptable error budget associated with their system design and purchase system components with appropriate accuracy specifications. The accuracy specification attributed to an electronic component is the indicator of how much error can be expected in a particular component ...

Signal Conditioning Article

This month's Control Engineering (Jan'04) contains a good article on "Signal Conditioning - Why and How". It explores a few often overlooked reasons to use signal conditioning modules (SCM's).

Sampling Rates and THE LAW

Nyquist criterion demands that we sample at GREATER THAN twice the highest frequency applied to our analog-to-digital converter (A/D). This is required to avoid aliasing errors from the A/D. Following this LAW will provide enough meaningful information from our A/D to determine the frequency content in the measured signal.

System Throughput

"Hello, that looks like an interesting data acquisition system! How fast is it and how much does it cost?" Apparently, simple questions that unfortunately, require complex answers! Yes, there are no simple answers to how fast and how much!

Easy Recalibration Procedure

How would you like a simple, single-page instruction to recalibrate your signal conditioners? How would you like to be able to recalibrate the zero point and then recalibrate the span without going back to readjust the zero and then again adjust the span, and then the zero ... you get the picture!

Surge Withstand Capability

Electrical surges due to lightening storms, brownouts, power interruptions, etc often cause catastrophic failures in electronic equipment. These surges can occur between any two wires; supply lines and earth ground, supply lines and common return (the white wire) and between individual supply lines.

Reproducibility - Repeatability

Equally important to the dollar budget is the error budget, which is often overlooked or determined de facto by cost constraints. For optimum system performance, each individual system element needs an acceptable error allocation. In determining system error budgets, "repeatability" is often confused with "reproducibility".

Linearity and Conformity

Data acquisition and process control systems function more efficiently and are easier to install if their field inputs are supplied by sensor signal conditioning modules which have linear transfer functions.

Using Ethernet for Data Acquisition

Networking engineers continue to have questions regarding the efficacy of Ethernet and where it comes down regarding determinism. Is it or isn't it deterministic?

3-Phase AC Calculations Revisited

This 3-phase application note is a continuation of Dataforth's Application Note AN109 which contains Single-Phase system definitions and basic rules for calculations. Both Single and Three-Phase documents include interactive Excel spreadsheets.

Single Phase Revisited

All things change, nothing last forever; so they say. Electronic equipment changes in behavior are due to a variety of factors. For example, moisture, temperature, and age are just a few such factors...

Industrial Data Acquisition

So what does industrial data acquisition really mean? Sure, you want the device to be rugged, able to handle hostile temperatures and electrical environments. Of course, the device must be very reliable! ...

Failure Rates

How long can one expect an electronic unit to survive? The answer to that question is based on a statistical parameter called "failure rate". If one knows the failure rate of a device, then how long before the unit fails can be statistically predicted...

Drift Specs

All things change, nothing last forever; so they say. Electronic equipment changes in behavior are due to a variety of factors. For example, moisture, temperature, and age are just a few such factors...

Input Resistance

All instrumentation modules, which actively gather data, must extract energy from sensors in order to measure information. This "energy extraction" will, of course, create serious errors if allowed to be excessive. We see the significance of this error reflected as "input" specifications of signal conditioning modules.

When Good Grounds Go Bad

Our article covers the common topologies used in industry to connect single-phase and three-phase systems. We describe and show how voltage distribution panels 'distribute' working voltages as well as neutral and ground wire connections.

Programmable Signal Conditioning

Dataforth designs and builds "Instrument Class" fixed function conditioners that provide 0.03% accuracy. We also make programmable signal conditioners that provide a typical 0.1% accuracy from any voltage, current, thermocouple, or RTD input type and input range.

Signal Conditioning Tutorial

Dataforth's twenty-six page signal conditioning tutorial has been a popular handout! So, we've turned it into an Adobe pdf file that you can now download and print or reference at your convenience....

DIN or 5B/7B Option

You have a choice. More and more we hear how DIN is IN! We see how manufacturers have packaged many of their new products in DIN mount enclosures ...

5B or 7B

Comparison of 5B and 7B signal conditioning modules: If you're familiar with 5B signal conditioners, you might not be familiar with 7Bs, or if you've used 7Bs you may not know about 5Bs ...

Thermocouples

Our application notes "Introduction to Thermocouples" and "Using Thermocouples", we explore the history of thermocouple technology and look at some modern day specs ...

Common Mode Voltage

Dataforth's isolated signal conditioners are designed with a patented isolation barrier that results in a common mode gain specification that is INDEPENDENT of the module's differential gain! ...

Signal Conditioner Life

In order to understand MTBF (Mean Time Between Failures) it is best to start with something else -- something for which it is easier to develop an intuitive feel. ...

Transient Protection

Industrial equipment located in the "field" is exposed to electrical noise, power surges, and transient events such as static discharge or even, near by lightning strikes. An Instrument ClassTM Signal Conditioner from Dataforth provides ...

Analog-to-Serial

Introducing the new SCM9B-D100 Series of isolated and software configurable single-channel data acquisition modules.

Why True RMS?

Application Note, AN101, is a six (6) page, in depth, presentation of why RMS (the Root-Mean-Square) approach is used to accurately determine effective values of voltage or current in AC signals.

System Accessories

We recommend a keep-it-simple approach when building a new test and measurement or data acquisition system. Approach your requirements from the sensor side and then move on up to the computer or controller end.

New Application Note, AN104

Last Newsletter we reviewed a Dataforth 2-Wire transmitter product ... This time we offer an excellent Application Note all about 2-Wire, 4-20mA, applications!

Measuring True RMS

Just like using a hand-held multimeter to read AC voltages and currents, you can install a DIN package "Instrument Class(tm)" module in your control system to measure and present that same RMS data...

Test Reports

Are you sure that your signal conditioners are performing properly? You need to be sure because ...

Loop Isolators

We've had lots and lots of application questions since Dataforth introduced its new family of loop isolators last year! ...

Isolated I/O to Serial Data

Over 75% of the industrialized world still uses RS-232 or RS-485 serial data communications to acquire process variable information and to control associated electrical / electronic systems...

Serial Data

From all the articles on "fieldbuses", that is - Profibus, DeviceNet, CAN, ModBus, and others, one would think that these busses dominate. NOT TRUE! Good old RS-232 and RS-485 are still used in over 75% of process control networks...

It's about isolation & protection...

Here's a good analog I/O refresher -- our new seven page white paper tells you everything you need to know about solving problems of ...

Quick Reference

... for RS-232C, RS-422, RS-423, RS-485 ...