Lake Shore Cryotronics 121, Руководство пользователя

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2.7.2 Sensor Lead Cable
The sensor lead cable used outside the cooling system can be much dif-
ferent from what is used inside. Between the instrument and vacuum
shroud, heat leak is not a problem, but errors from noise pick up need to
be minimized. Larger conductor, 22 to 28 AWG stranded copper wire is
recommended because it has low resistance yet remains flexible when
several wires are bundled in a cable.
The arrangement of wires in a cable is also important. For best results,
use twisted pair, shielded cable. This type of cable is available through
local electronics suppliers. Instrument specifications are given assuming
3 m (10 ft) of sensor cable. Longer cables, 30 m (100 ft) or more, can be
used but environment conditions may degrade accuracy and noise spec-
ifications.
2.7.3 Grounding and Shielding Sensor Leads
The Model 121 does not provide ground referenced leads. This means
that I+ and I- cannot be attached to ground in any configuration. The
standard power supply (109-132) does not carry earth ground through
to chassis. To meet the accuracy specifications at lower current levels the
Model 121 must be in a properly shielded system. Since the Model 121 is
not connected to earth ground it is important to tie it to measurement
common. This connection can be made externally through the chassis
FIGURE 2-4 Output connector
Pin Symbol Description
1 I+ Current out
2 I– Current return
TABLE 2-2 Output current connector details