2600A_ThermalGuide_AppNote

2600A_ThermalGuide_AppNote
Number 3015
Application Note
Se­ries
Thermal Guidelines for Rack-Mounting
Series 2600/2600A Instruments
in accordance with the following restrictions. Refer to Figures 2
and 3 for instrument placement options.
This document defines the environment needed to ensure
proper instrument cooling when placing multiple Series
2600/2600A System SourceMeter® instruments in a racked
configuration. Power requirements for running multiple
instruments are also included to ensure an adequate power
supply is available.
• Units may be rack-mounted side by side.
• All rows of instruments are to be placed with 1U space
above the units.
Cabinet Specifications
• Spaces between units are to be filled with vented panels
having a minimum open air ratio of 33%.
The cabinet used must meet IEC 19-inch rack specifications.
Refer to Figure 1 for the preferred cabinet dimensions.
• The top row of instruments must also have 1U space above
it to allow for proper air flow across the unit.
The cabinet must be capable of exhausting 600CFM of air
from its bottom. This air flow can be achieved by using multiple
fans or blower(s) as long as the combined total air flow is
600CFM.
• All rack spaces not occupied by an instrument or vent panel
must be filled with solid blank panels.
• The rear door of the cabinet (if applicable) is to be closed.
The cabinet shall not have a front door.
Instrument Placement in Cabinet
To avoid overheating or damage to instruments, all Series
2600/2600A System SourceMeter products must be rack-mounted
Front
Side
64.75
(37U)
19.0
Figure 1. Cabinet dimensions
• All cable entry or exit ports are to be sealed to close off the
flow of air.
28.0
The perimeter of all instruments is to be sealed to restrict air
flow, as shown in Figures 2 and 3.
Solid blank panel
Solid blank panel
Perimeter of
instruments to
be sealed to
restrict air flow
Emergency Off Switch
Emergency Off Switch
Series 2600 Instrument
Solid blank panel
1U vent panels
above instruments
Perimeter of
instruments to
be sealed to
restrict air flow
1U vent panels
above instruments
Series 2600 Instrument
Power Distribution Unit
(reference only)
Figure 2
Power Distribution Unit
(reference only)
Figure 3
Thermal Characteristics
The placement of vented panels and sealed openings is critical
to the performance of Series 2600/2600A System SourceMeter
instruments. Figure 4 depicts the flow of air into the top of each
instrument and out of the rear. The air flow created by the fan(s)
or blower(s) in the bottom of the cabinet draws cool air into the
instruments and forces the hot air out the bottom of the cabinet.
If the ambient temperature exceeds the internal threshold
of the unit, the unit may overheat. Overheating occurs when
the internal temperature of the Series 2600/2600A System
SourceMeter instrument is exceeded, causing the instrument’s
channel output to turn off and go into standby mode until the
instrument’s temperature drops below this limit.
There are a variety of common causes of overheating:
• Allowing openings in the cabinet such as cable ports, rear
door, auxiliary vents, removed side panels, etc.
• Failing to seal off the perimeter around the instruments.
• Failing to remove the front door of the cabinet.
• Exceeding the power output on each channel (see power
equation and table in Figure 3). Refer to the Series
2600/2600A System SourceMeter Reference Manual for
output derating due to ambient temperature.
Figure 4
Equations apply to both channels, sinking or sourcing power
simultaneously. If a duty cycle less than 100% is required to avoid
overheating, the maximum on time must be less than 10 seconds.
General SourceMeter Power Equation
(VOA − VP )(I P)
DC MAX + (VOA − V B)(I B) ≤ (PCS − PDER )
PCS = The maximum power generated in a SourceMeter channel that can be properly
dissipated by the SourceMeter cooling system.
TAMB = The ambient temperature of the SourceMeter operating environment.
PDER = TAMB – 30
• This factor represents the number of watts the SourceMeter instrument is de-rated
when operating in environments above 30°C. This is represented as a temperature
because the maximum output power of each SourceMeter channel is reduced by
1W per degree C above 30°C.
• PDER is 0 when the ambient temperature is below 30°C.
VOA = The SourceMeter output amplifier voltage. This constant can be found in the tables
below.
VP =
The voltage level the SourceMeter instrument is attempting to force while at the
pulse level.
• When operating in quadrants 1 or 3 (sourcing power), the sign of this voltage must
be positive when used in the power equations.
VB =
The general SourceMeter power equation and the maximum
duty cycle equation are taken from Keithley Instruments’ 2600A
Reference Manual.
Examples
Refer to Section 8 of the 2600/2600A System SourceMeter®
Reference Manual for further examples.
Instrument
2601A
2602A
2611A
2612A
2635A
2636A
Max Source Value
(into a short: continuous)
6.0V 1.5A
6.0V 1.5A
20.0V 1.0A
20.0V 1.0A
20.0V 1.0A
20.0V 1.0A
Example
40.4W ([email protected] or
[email protected])
30.3W ([email protected] or
[email protected])
• When operating in quadrants 2 or 4 (sinking power), the sign of this voltage must be
negative when used in the power equations.
Power Consumption
The voltage level the SourceMeter instrument is attempting to force while at the
bias level.
Refer to 2600/2600A System SourceMeter instrument VA ratings
for the total power draw in your system. Adequate power
distribution can then be specified to meet your specific needs.
• When operating In quadrants 1 or 3 (sourcing power), the sign of this voltage must
be positive when used in the power equations.
• When operating in quadrants 2 or 4 (sinking power), the sign of this voltage must be
negative when used in the power equations
IP =
The current ftowing through the SourceMeter channel while at the pulse level.
IB =
The current ftowing through the SourceMeter channel while at the bias level.
Instrument
2601A
2602A
2611A
2612A
2635A
2636A
Power Draw (VA)
240
240
240
240
250
250
Specifications are subject to change without notice.
All Keithley trademarks and trade names are the property of Keithley Instruments, Inc.
All other trademarks and trade names are the property of their respective companies.
A
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O F
C O N F I D E N C E
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© Copyright 2009 Keithley Instruments, Inc.
Printed in the U.S.A.
No. 3015
03.4.09
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