1. Instrumentation & Measurement (ME342)
Chapter 8: Display, Recording, and Presentation of Measurement Data
Dr. Hani Muhsen

2. 8.1 Introduction
After describing ways of producing high-quality, error-free data at the output of a measurement system, the next consideration is how to present it in a form where it can be readily used and analyzed..
techniques available to either display measurement data for current use.
Techniques to record measurement data for future use.

3. 8.2 Display of Measurement Signals
Measurement signals in the form of a varying electrical voltage can be displayed either by an oscilloscope or by any of the electrical meters.
Other options:
Electronic Output Displays
Computer Monitor Displays
Examples of Electronic Displays ( )
Computers are now both inexpensive and highly reliable and provide an excellent mechanism for both displaying and storing information.
Touch screens have the ability to display the same sort of information as a conventional computer monitor, but also provide a command-input facility.
Figure 8.1 Character formats used in electronic displays: (a) seven segment and (b) 7 × 5 dot matrix.

4. Figure 8.2 Original form of galvanometric chart recorder.

5. 8.3 Recording of Measurement Data
Potentiometric Recorder
Reduces inaccuracy to ±0.1% compared to ±2% in a galvanometric mechanism recorder
Typical resolution 0.2% of the full-scale reading
Slow response time seconds (suitable for measuring d.c. and slowly time- varying signals)
-Originally, the servo motor was a standard d.c. motor, but brushless servo motors are now invariably used to avoid the commutator problems that occur with d.c. motors.
-The position signal is measured by a potentiometer in less expensive models, better ones use noncontacting ultrasonic sensor.
Figure 8.3 Servo system of a potentiometric chart recorder.

6. Forms of Potentiometric Chart Recorder
Pen strip chart recorder (hybrid chart recorder)
Includes a microprocessor controller.
The paper chart moves at different speeds (fastest 6000mm/hr and slowest 1mm/hr)
up to 3 inputs & up to 3 pens in different colors.
Figure 8.4 Honeywell DPR100 strip chart recorder.
Multipoint strip chart recorder
Uses a dot matrix print head striking against an ink ribbon instead of pens.
Allows for up to 24 different signal inputs to be recorded simultaneously using a 6-color ink ribbon.
Previously called hybrid due to microprocessor
Microprocessor: change range.. Change speed.. Set alarms
Additional printing alpha numeric (like date time info) and digital displays
Chart paper comes in either roll or fan-fold form

7. Forms of Potentiometric Chart Recorder
Heated-stylus chart recorder
Records input signal by applying a heated stylus to heat-sensitive chart paper.
Used to avoid problem of pen cartridges or printer ribbons running out of ink experienced in other forms of paper based chart recorders.
Circular chart recorder
Consists of servo-driven pen
Rotational speed of chart between 1 rev/ hr to 1 rev in 31 days
Compactness
Up to 4 different signals
Figure 8.5 Circular chart recorder.

8. Forms of Potentiometric Chart Recorder
Paperless chart recorder
Also called virtual chart recorder or a digital chart recorder .
Displays the time history of measured signals electronically using a color- matrix liquid crystal display.
No need for chart paper or ink. Reliable.
Only displays one screen full of info at a time.
Screen display motion between 1 & 6000 mm/hr AND Typical inaccuracy less than ±0.1%

9. Forms of Potentiometric Chart Recorder Videographic recorder
8.3.2 Ink-Jet and Laser Printers
A computer is a routine part of many data acquisition operations  output data to a computer printer rather than chart recorder
Saves cost and is facilitated by the availability of ready software that can output data in a graphical format.
8.3.3 other recording instruments
Data logging acquisition devices
Digital storage oscilloscope
Forms of Potentiometric Chart Recorder
Videographic recorder
Provides the same facilities as a paperless chart recorder with additional display modes, such as bar graphs (histograms) and digital numbers.

10. 8.3.4 Digital Data Recorders
Also known as data loggers
Recorded data can be transferred to a computer for further analysis, displayed, or recorded on a hard copy.
Handle both analogue and digital signals (a.c. voltages, a.c. currents, d.c. voltages, d.c. currents, discrete data from switch closures or relay operations)
The quality of the data recorded by a digital recorder is a function of the cost of the instrument.
More memory providing a greater data storage capacity
greater resolution in the A/D converter to give better recording accuracy
Faster processing to allow greater data sampling frequency
Dr. Jumana: A data logger is a DAQ but a DAQ is not necessarily a data logger.. Data loggers have a slower sampling rates and they don’t have to be connected to a computer.. While DAQ is connected to a computer.. Data logger is a stand alone device.. For example Labview is an example of software for DAQ not Data logger.. An example of Data logger is seismic activity monitoring research center
Data loggers have real time clocks and they record large data, while Labview doesnot necessarily qcquire dta using a real clock (but has the option to be synced)

11. 8.4 Presentation of Data
Two forms available for presenting data on paper are: Tabular and Graphical
8.4.1 Tabular Data presentation
Allows data values to be recorded in a precise way that exactly maintains the accuracy to which the data values were measured. Also contain further values calculated from raw data.

12. 8.4 Presentation of Data 8.4.2 Graphical presentation of DATA
Involves some compromise in the accuracy
to which data are recorded, as the exact
values of measurements are lost.
Figure 8.6 Sample graphical presentation of data: graph of stress against strain.

13. Graphical Vs. Tabular data presentation
Graphs provide pictorial representation of results that is comprehended more readily than tabular results.
Graphs are useful for expressing the quantitative significance of results and showing whether a linear relationship exists between two variables.
Graphs can sometimes show a data point that is clearly outside the straight line indicating it’s due to human error of momentary malfunction in the instrument.

14. Fitting Curves to data points on a graph
Drawing a straight line (or smooth curve) that passes close to all data points on a graph, is justified since random errors are known to affect measurements.
Any line between data points is mathematically acceptable as a graphical representation of data if the maximum deviation of any data point from the line is within the boundaries of the level of possible measurement error.
Within the range of possible lines that can be drawn only one line is the optimum one; where the sum of negative errors in data points on one side of the line is balanced by the sum of positive errors in data points on the other side of the line.
An approximation of the optimum can be obtained by drawing a line through the data points by eye.
In some cases it is necessary to fit a line mathematically, using regression techniques.