Heater Output Setup; Heater Output Description; Heater Output Connectors; Heater Output Wiring - Lakeshore 335 User Manual

36 c 3: Installation
HAPTER
3.7 Heater Output
Setup
3.7.1 Heater Output
Description
3.7.2 Heater Output
Connectors
3.7.3 Heater Output
Wiring
Model 335 Temperature Controller
The following section covers the heater wiring from the vacuum shroud to the instru-
ment for both heater outputs. Specifications are detailed in section 1.3. For help on
choosing and installing an appropriate resistive heater, refer to section 2.5.
Output 1 and Output 2 in current mode are traditional control outputs for a cryogenic
temperature controller. Both are variable DC current sources with software settable
ranges and limits. Both are configurable for optimization using either a 25 ) or a 50 )
heater resistance. At the 50 ) setting, Output 1 is limited to 1 A (50 W), and Output 2
is limited to 0.707 A (25 W). At the 25 ) setting, the maximum heater output current
is 1.732 A (75 W) for Output 1 and 1 A (25 W) for Output 2 (if Output 1 is set to
50 W or less).
The compliance voltage of Output 1 is 50 V minimum, but can reach as high as 58 V if
the heater resistance is higher than the nominal setting, and the compliance voltage
of Output 2 is 35.4 V minimum, but can reach as high as 41 V if the heater resistance is
higher than the nominal setting. Heater power is applied in one of three ranges: high,
med, or low. Each range is one decade lower in power. Refer to TABLE 4-11 for maxi-
mum current and power ratings into different heater resistance.
Dual banana jacks on the rear panel of the instrument are used for connecting wires
to the heater outputs. Two standard dual banana plug mating connectors are
included in the connector kit shipped with the instrument. This is a common jack and
additional mating connectors can be purchased from local electronic suppliers, or
from Lake Shore as P/N 106-009. The heater is connected between the HI
and LO terminals.
FIGURE 3-8 Rear panel showing

heater output connectors

Heater output current is what determines the size (gauge) of wire needed to connect
the heater. The maximum current that can be sourced from heater Output 1 is
1.732 A. When less current is needed to power a cooling system, it can be limited with
range settings.
When setting up a temperature control system, the lead wire for the heater must be
capable of carrying a continuous current that is greater than the maximum current.
Wire manufacturers recommend 26 AWG or larger wire to carry 1.732 A of current,
but there is little advantage in using wire smaller than 20 AWG to 22 AWG outside the
cryostat. Inside the cryostat, smaller gauge wire is often desirable.