User manual

User Manual
17
4: If (X<=>F) (P89)
1: 4 X Loc [ RH ]
2: 4 <
3: 103 F
4: 30 Then Do
5: Z=F x 10^n (P30)
1: 100 F
2: 0 n, Exponent of 10
3: 4 Z Loc [ RH ]
6: End (P95)
7: End (P95)
8: If time is (P92)
1: 0 Minutes (Seconds --) into a
2: 60 Interval (same units as above)
3: 10 Set Output Flag High (Flag 0)
9: Set Active Storage Area (P80)
1: 1 Final Storage Area 1
2: 101 Array ID
10: Real Time (P77)
1: 1220 Year,Day,Hour/Minute (midnight = 2400)
11: Average (P71)
1: 1 Reps
2: 3 Loc [ AirTC ]
12: Sample (P70)
1: 1 Reps
2: 4 Loc [ RH ]
10. Measuring Probes with Long Cables
For cable lengths longer than 6.1 m (20'), CSI recommends measuring the
voltage signals using differential inputs as discussed below. Connections for
differential inputs are given in Table 8-2.
The signal reference (yellow) and the power ground (grey) are in common inside
the HC2S3. When the HC2S3 temperature and relative humidity are measured
using a single-ended analogue measurement, both the signal reference and
power ground are connected to ground at the datalogger. The signal reference
and power ground both serve as the return path for power. There will be a
voltage drop along those leads because the wire itself has resistance.
The HC2S3 draws approximately 2 mA when powered with 12V. The wire
used in the HC2S3 (P/N #27746) has resistance of 14.74 Ω/304.8 m (1000').
Since the signal reference and the power ground are both connected to ground at
the datalogger, the effective resistance of those wires together is half of
14.74 Ω/304.8 m (1000'), or 7.37 Ω/304.8 m (1000'). Using Ohm’s law, the
voltage drop (V
d
), along the signal reference/power ground, is given by Eq. (1).