Test
Testo 650 /
0628.0024
EminTech
+ durable industrial design
+ battery voltage indicator
- significant instability
- results outside specification
- inadequate manual
- extra charge for calibration
instructions
The device is sold as two separate parts. The instrument Testo 650, that may also be used for other purposes, and the sensor 0628.0024.
The design submitted a feeling of high industrial quality.
Lots of metal and well dimensioned plastic gave weight and an instrument that appeared to deliver also in tough environments. After completion of measurements, during instrument power down, the battery voltage was displayed.
Manual
The manual for the instrument Testo 650 covered a lot of features for the instrument, like e.g. attaching an optional printer. No information about the use of the probe 0628.0024 was however included.
Calibration
Both instrument and sensor were delivered with calibration certificates. For further validations, instructions of how to calibrate the instrument was only supplied after buying a
calibration kit (about € 220).
Measurement results
The measurements were easily accomplished.
The results were, however, disappointing.
As seen in the diagram below, the results varied significantly
for NaCl (0.755 aw). For each measurement series the read result increased by more than 0.01 aw.
Additional measurements and other salt samples confirmed
this behaviour. The results for NaCl samples varied between 0.771 and 0.791.
Resting the sensor for 6 days gave 0.772 for a NaCl sample.
It appears that other phenomena than sensor saturation were responsible for the result variations.
At aw values higher than 0.97, the results were unreliable,
in spite of the stated measurement interval 0 - 1.000 aw.
A cut-off in the instrument showed the result 0.999,
irrespective of sample aw = 0.975, 0.996 or 1.000.
The cut-off gave a maximal error in the three samples
of 0.024, 0.003 and -0.001, respectively.
The apparent low deviations at aw higher than 0.95 in the diagram shown below are hence not true observations but results of this cut-off.
| Links | |
| Swe.agent | |
| Price € | ~ 2 400 |
| Specification | |
| Accuracy | 0.01 aw |
| Range | 0 - 1.000 aw |
| Calibration | |
| Instructions | Optional |
| Samples | Optional |
| Own media | ? |
| Other | |
| Manual | Yes, inadequate |
| in Swedish | No |
| Computer interface |
Yes, with optional software |
