Technique |
90° modulated infra-red (ISO7027). |
Ranges |
40, 100, 400 and 1,000NTU - range selection
set by user, initially set at 100NTU. Other
range values available at additional cost up to
3,000NTU. |
Resolution |
Range:
40NTU
100NTU
400NTU
1000NTU
|
RS232/SDI-12: ±0.01NTU
±0.02NTU
±0.1NTU
±0.2NTU
|
Analogue:
±0.06NTU
±0.15NTU
±0.60NTU
±1.50NTU
|
Repeatability |
±1% at 25°C. |
Linearity |
Better than 1% for 40NTU, 100NTU and 400NTU, 3% for 1,000NTU. |
Temperature Coefficient |
Better than ±0.05%/°C. |
Repeatability |
±1% at 25°C |
Linearity |
Better than 1% for 40NTU, 100NTU and
400NTU, 3% for 1,000NTU |
Temperature Coefficient |
Better than ±0.05%/°C |
Outputs |
All models - RS232 - 1200BPS, 7 data bits,
even parity, one stop bit.
NEP390/395 - SDI-12 Protocol (V1.3).
NEP391/396 - Analogue Voltage (0-1V or 0-
2.5v), minimum load 3kohms and Analogue
Current (4-20mA or 0-20mA), maximum load
350 ohms. |
Measurements |
RS232 and SDI-12 interfaces
Latest turbidity measurement -1 sample.
Mean and Sample Variance (over 100 samples).
Median (over 100 samples).
Minimum (over 100 samples).
Maximum (over 100 samples).
Probe supply voltage.
Probe internal temperature.
Analogue Interface
Analogue representation of the level of
turbidity as a proportion of the range selected.
Approximate update rate is 0.5 seconds. Voltage
and current outputs operate concurrently. |
Calibration |
2 or 3 point calibration for each range.
May be set by the user only through the RS232 interface and for the range selected.
Can revert back to factory calibration settings
after user calibration. |
Power |
9.6 - 16V dc, 35mA ON. 60mA ON and wiping for NEP395 and NEP396 only. STANDBY of 1.5mA on NEP390 and NEP395 only.
Add a provision for an additional 20mA for the
NEP391/396 if the 0/4-20mA output is used. |
Wiping |
Initiated by wipe or autowipe $ commands
under the RS232 interface or M8! command
under SDI-12 or for the NEP396 only it can be
externally initiated by momentarily (>50msecs)
bringing the RS232RX conductor to the 0V
conductor. |
Wipe Time |
6 seconds nominal. |
Weight |
NEP390/391 - 500gms - probe only, 100gms
connector plus 70gms per meter of cable.
NEP395/396 - 550gms - probe only, 100gms
connector plus 70 gms per meter of cable. |
Dimensions |
NEP390/391- 250mm long unmated, 321mm
long mated to end of protective boot, 32m dia.
NEP390G/391G- 292mm long including
glanding and strain relief assembly, 32mm
diameter.
NEP395/396- 256mm long unmated, 327mm
long mated to end of protective boot, 32m dia.
NEP395G/396G- 299mm long including
glanding and strain relief assembly, 32mm
diameter |
Construction |
Stainless steel casing with protruding
castellations to protect the plastic fibre-optic
face.
Cable connection via 7-way waterproof
connector (standard version), or probe cable is
glanded directly from the rear of the probe via
an integrated plastic strain relief (add suffix G to
standard version). |
Cable |
NEP390/395 - 5 core + shield, 6mm dia. PUR
sheath . Conductor resistance 45 ohms per km.
NEP391/396 - 7 core + shield, 6.5mm dia. PUR
sheath. Conductor resistance 75 ohms per km. |
Cable Length |
To order - 60m (200ft) maximum for NEP390/
395, 99m (330ft) maximum for NEP391/396. |
Depth Rating |
100m (330ft) |
Operating Temperature |
-10°C to 40°C |
Storage Temperature |
-20°C to 50°C |