Monday, February 24, 2014

Selection of measuring devices

The following points are helpful when selecting most of measuring devices:



Storage conditions:
Storage temperature and humidity

Working conditions:
Ambient temperature range
Humidity range

Sensitivity:
The minimum unit | step of measurement

Maximum measurement value

Auto-range or manual range:
Auto-range is preferred for non-professionals and for time saving

Resolution:
The number of right digits that can be displayed

Display | Screen type:
- Mon-color
- 7 segment or 15 segment display
- Dot matrix display
- Color display

Display | screen size:
The dimensions of screen

Display graph

Measuring units:
Different measuring units save the time of unit conversion

Response time | Stabilization time:
Time needed to reach the true value.

Hardware overload protection

Accuracy:
Tolerance of measurement +/- as an absolute value of a percentage of full scale reading. How much far the measured value from the actual value.

Precision | Repeat-ability:
How often the reading is repeated or how near the measured values.



Linearity:
How the electric signal is varying with the measure physical property. The higher the linearity, the lower number of points needed for calibration.

Sampling time:
The frequency of updating measurements

Recording/logging

Internal memory size:
Internal memory size for storing measured values

Power source:
- Direct AC current (internal adapter).
- Voltage range and frequency
- AC current with adapter
- Internal battery:
- Battery life
- Maximum battery on time
- Internally-recharged
- Externally recharged

On-screen battery indicator

Ruggedness:
The maximum drop distance after which the device malfunctions or is destroyed

Auto-power off time

Portability

Calibration:
-Has traced calibration certificate from NIST
-Can be calibrated: offsets can be saved in the device

Computer interface connection:
- RS 232
- USB
- HDMI
- Wireless

Computer software
- Device configuration from PC

PC-Online reading | recording

Open channel/not connected probes | sensors detection

Wrong probes | sensors connection detection:
This function is useful in multiple-function measuring devices

Replaceable overload protection

Device sealing | Keypad sealing

Device mounting options:
- Adjustable legs
- Magnetic -mount
- Screw mount

External Vs. internal sensor

Taring | Zeroing

Hold manual Vs. Automatic

Minimum, maximum, average

Counting:
This feature is available in tachometers, and balances

Programmable limit alarm

Buzzer sound quality

Probe length

Probe dimensions