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

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

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

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.

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


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

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

Auto-power off time


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

Computer interface connection:
- RS 232
- 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

This feature is available in tachometers, and balances

Programmable limit alarm

Buzzer sound quality

Probe length

Probe dimensions