RayTek MARATHON MR Operating Instructions Manual

MARATHON

MR

2-Color Infrared Thermometer

Operating Instructions

Rev. E2 04/2011

56913

Contacts

Raytek Corporation
Worldwide Headquarters

Santa Cruz, CA USA
Tel: [phone] – 8074 (USA and Canada only)
+1 831 458 – 3900

[e-mail]

European Headquarters
Berlin, Germany

Tel: [phone]

[e-mail]

France

[e-mail]

United Kingdom

[e-mail]

China Headquarters
Beijing, China
Tel: [phone]

[e-mail]

Internet: http://www.raytek.com/

Thank you for purchasing this Raytek product. Register today at www.raytek.com/register to receive
the latest updates, enhancements and software upgrades!

© Raytek Corporation.

Raytek, DataTemp and the Raytek Logo are registered trademarks of Raytek Corporation.
All rights reserved. Specifications subject to change without notice.

WARRANTY

The manufacturer warrants this instrument to be free from defects in material and workmanship
under normal use and service for the period of two years from date of purchase. This warranty
extends only to the original purchaser. This warranty shall not apply to fuses, batteries, or any
product that has been subject to misuse, neglect, accident, or abnormal conditions of operation.

In the event of failure of a product covered by this warranty, the manufacturer will repair the
instrument when it is returned by the purchaser, freight prepaid, to an authorized Service Facility

within the applicable warranty period, provided manufacturer’s examination discloses to its

satisfaction that the product was defective. The manufacturer may, at its option, replace the product in
lieu of repair. With regard to any covered product returned within the applicable warranty period,
repairs or replacement will be made without charge and with return freight paid by the manufacturer,
unless the failure was caused by misuse, neglect, accident, or abnormal conditions of operation or
storage, in which case repairs will be billed at a reasonable cost. In such a case, an estimate will be
submitted before work is started, if requested.

THE FOREGOING WARRANTY IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY IMPLIED WARRANTY OF
MERCHANTABILITY, FITNESS, OR ADEQUACY FOR ANY PARTICULAR PURPOSE OR USE.
THE MANUFACTURER SHALL NOT BE LIABLE FOR ANY SPECIAL, INCIDENTAL OR
CONSEQUENTIAL DAMAGES, WHETHER IN CONTRACT, TORT, OR OTHERWISE.

SOFTWARE WARRANTY

The manufacturer does not warrant that the software described herein will function properly in every
hardware and software environment. This software may not work in combination with modified or
emulated versions of Windows operating environments, memory-resident software, or on computers
with inadequate memory. The manufacturer warrants that the program disk is free from defects in
material and workmanship, assuming normal use, for a period of one year. Except for this warranty,
the manufacturer makes no warranty or representation, either expressed or implied, with respect to
this software or documentation, including its quality, performance, merchantability, or fitness for a
particular purpose. As a result, this software and documentation are licensed “as is,” and the licensee
(i.e., the User) assumes the entire risk as to its quality and performance. The liability of the
manufacturer under this warranty shall be limited to the amount paid by the User. In no event shall
the manufacturer be liable for any costs including but not limited to those incurred as a result of lost
profits or revenue, loss of use of the computer software, loss of data, the cost of substitute software,
claims by third parties, or for other similar costs. The manufacturer’s software and documentation are
copyrighted with all rights reserved. It is illegal to make copies for another person.

Specifications subject to change without notice.

The device complies with the requirements of the European Directives.

EC – Directive 2004/108/EC (EMC)

TABLE OF CONTENTS

1 SAFETY INSTRUCTIONS .............................................................................................................................. 7

2 PRODUCT DESCRIPTION ............................................................................................................................ 8

2.1 THEORY OF OPERATION FOR 2-COLOR SENSORS ......................................................................................... 9

2.1.1 Partially Obscured Targets ................................................................................................................... 9

2.1.2 Targets Smaller Than Field of View ...................................................................................................... 9

2.1.3 Low or Changing Emissivities ............................................................................................................ 10

3 TECHNICAL DATA ....................................................................................................................................... 11

3.1 MEASUREMENT SPECIFICATIONS ............................................................................................................... 11

3.2 GENERAL SPECIFICATIONS ......................................................................................................................... 13

3.3 ELECTRICAL SPECIFICATIONS ..................................................................................................................... 14

3.4 DIMENSIONS ............................................................................................................................................... 14

3.5 OPTICAL SPECIFICATIONS .......................................................................................................................... 16

3.6 SCOPE OF DELIVERY .................................................................................................................................... 17

4 ENVIRONMENT ............................................................................................................................................ 18

4.1 AMBIENT TEMPERATURE ............................................................................................................................ 18

4.2 ATMOSPHERIC QUALITY ............................................................................................................................. 18

4.3 ELECTRICAL INTERFERENCE ....................................................................................................................... 18

5 INSTALLATION ............................................................................................................................................ 19

5.1 MECHANICAL INSTALLATION .................................................................................................................... 19

5.1.1 Distance to Object ............................................................................................................................... 19

5.1.2 Sensor Placement (1-Color Mode) ...................................................................................................... 19

5.1.3 Sensor Placement (2-Color Mode) ...................................................................................................... 20

5.1.4 Viewing Angles ................................................................................................................................... 21

5.1.5 Aiming and Focusing .......................................................................................................................... 22

5.2 ELECTRICAL INSTALLATION ....................................................................................................................... 23

5.2.1 DIN Connector Wiring ....................................................................................................................... 23

5.2.2 Cables and Terminal Block .................................................................................................................. 23

5.2.3 Power Supply ...................................................................................................................................... 25

5.2.4 PC Connection via USB/RS485 Converter ......................................................................................... 26

5.2.5 PC Connection via RS232/485 Converter .......................................................................................... 27

5.2.6 Addressing .......................................................................................................................................... 29

6 OPERATION ................................................................................................................................................... 30

6.1 CONTROL PANEL ........................................................................................................................................ 30

6.2 OPERATION MODES .................................................................................................................................... 31

6.2.1 Temperature Display ........................................................................................................................... 31

6.2.2 Emissivity (1-Color) ............................................................................................................................ 31

6.2.3 Slope (2-Color) .................................................................................................................................... 32

6.2.4 2C/1C Switch ...................................................................................................................................... 32

6.2.5 Overview to Hold Functions ............................................................................................................... 34

6.2.6 Setpoints .............................................................................................................................................. 35

6.2.7 Deadband............................................................................................................................................. 35

6.3 INPUTS AND OUTPUTS ............................................................................................................................... 36

6.3.1 Milliamp Output ................................................................................................................................ 36

6.3.2 Relay Outputs .................................................................................................................................... 36

6.3.3 Trigger ................................................................................................................................................ 36

6.4 FACTORY DEFAULTS .................................................................................................................................. 37

7 OPTIONS ......................................................................................................................................................... 38

7.1 WATER COOLED HOUSING INCLUDING AIR PURGE COLLAR .................................................................. 38

8 ACCESSORIES ............................................................................................................................................... 39

8.1 OVERVIEW .................................................................................................................................................. 39

8.2 FIXED MOUNTING BRACKET ...................................................................................................................... 39

8.3 AIR PURGE COLLAR ................................................................................................................................... 40

8.4 POLARIZING FILTER END CUP ................................................................................................................... 40

8.5 CABLES ....................................................................................................................................................... 41

8.6 INDUSTRIAL POWER SUPPLY ...................................................................................................................... 43

9 PROGRAMMING GUIDE ........................................................................................................................... 44

9.1 REMOTE VERSUS MANUAL CONSIDERATIONS .......................................................................................... 44

9.2 COMMAND STRUCTURE ............................................................................................................................. 44

9.3 TRANSFER MODES ...................................................................................................................................... 45

9.3.1 Poll Mode ............................................................................................................................................ 45

9.3.2 Burst Mode ......................................................................................................................................... 45

9.4 RESPONSE TIME IN SETUP MODE ............................................................................................................... 46

9.5 COMMAND LIST ......................................................................................................................................... 47

9.6 COMMAND EXAMPLES ............................................................................................................................... 49

10 MAINTENANCE .......................................................................................................................................... 50

10.1 TROUBLESHOOTING MINOR PROBLEMS .................................................................................................. 50

10.2 FAIL-SAFE OPERATION ............................................................................................................................ 50

10.3 CLEANING THE LENS ............................................................................................................................... 53

10.4 CHANGING THE WINDOW ....................................................................................................................... 53

11 APPENDIX..................................................................................................................................................... 54

11.1 DETERMINATION OF EMISSIVITY .............................................................................................................. 54

11.2 TYPICAL EMISSIVITY VALUES ................................................................................................................... 54

11.3 TYPICAL SLOPES ....................................................................................................................................... 56

11.4 2-WIRE COMMUNICATION ....................................................................................................................... 57

11.5 TRACEABILITY OF INSTRUMENT CALIBRATION ....................................................................................... 58

Safety Instructions

Marathon MR Rev. E2 04/2011 7

1

This document contains important information, which should be kept at all times with the instrument
during its operational life. Other users of this instrument should be given these instructions with the
instrument. Eventual updates to this information must be added to the original document. The
instrument can only be operated by trained personnel in accordance with these instructions and local
safety regulations.

Acceptable Operation

This instrument is intended only for the measurement of temperature. The instrument is appropriate
for continuous use. The instrument operates reliably in demanding conditions, such as in high
environmental temperatures, as long as the documented technical specifications for all instrument
components are adhered to. Compliance with the operating instructions is necessary to ensure the
expected results.

Unacceptable Operation

The instrument should not be used for medical diagnosis.

Replacement Parts and Accessories

Use only original parts and accessories approved by the manufacturer. The use of other products can
compromise the operation safety and functionality of the instrument.

Instrument Disposal

Do not dispose of this product as unsorted municipal waste. Go to Fluke’s website for

recycling information.

Operating Instructions

The following symbols are used to highlight essential safety information in the operation instructions:

Helpful information regarding the optimal use of the instrument.

Risk of danger. Important information!

Incorrect use of 110 / 230 V electrical systems can result in electrical hazards and personal
injury. All instrument parts supplied with electricity must be covered to prevent physical
contact and other hazards at all times.

Product Description

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The Marathon MR Series of instruments are 2-color infrared noncontact temperature measurement
systems with variable focus, through-the-lens sighting, and parallax-free optics. They are energy
transducers designed to measure accurately and repeatedly the amount of heat energy emitted from
an object, and then convert that energy into a measurable electrical signal. Temperature measurements
can be taken using either of the following modes:

1-color mode – for standard temperature measurements. The 1-color mode is best for

measuring the temperature of targets in areas where no sighting obstructions, either solid or
gaseous, exist. The 1-color mode is also best where the target completely fills the measurement
spot and where the background or foreground are higher in temperature than the target.

2-color mode – temperatures are determined from the ratio of two separate and overlapping

infrared bands. The 2-color mode is best for measuring the temperature of targets that are
partially obscured (either intermittently or permanently) by other objects, openings, screens, or
viewing windows that reduce energy, and by dirt, smoke, or steam in the atmosphere. The 2­color mode can also be used on targets that do not completely fill the measurement spot,
provided the background is much cooler than the target.

Each model operates as an integrated temperature measurement subsystem consisting of optical
elements, spectral filters, detector, digital electronics and a NEMA-4 (IEC 529, IP65) housing. Each is
built to operate on a 100 percent duty cycle in industrial environments. Outputs consist of
standardized current signals commonly available for use with computers, controllers, recorders,
alarms, or A/D interfaces.

Model

Temperature Range

Minimum Temperature
(95% Attenuation)

Optical Resolution
(Nominal)

Standard Focus

MR1SASF
MR1SBSF
MR1SCSF

600 to 1400°C (1112 to 2552°F)
700 to 1800°C (1292 to 3272°F)
1000 to 3000°C (1832 to 5432°F)

800°C (1472°F)
950°C (1742°F)
1300°C (2372°F)

44:1
82:1
130:1

Close Focus

MR1SACF
MR1SBCF
MR1SCCF

600 to 1400°C (1112 to 2552°F)
700 to 1800°C (1292 to 3272°F)
1000 to 3000°C (1832 to 5432°F)

800°C (1472°F)
950°C (1742°F)
1300°C (2372°F)

44:1
82:1
130:1

Focal Range SF = Standard Focus 600 mm to ∞ (24" to ∞)

CF = Close Focus 300 mm to 600 mm (12" to 24")

Table 1: Models

All Marathon sensors are addressable and can be used in multidrop environments. Setup, utility, and
operating/monitoring software is included with your sensor(s).

For the percentage of allowed signal reduction at temperatures below the minimum
temperature (95% attenuation) as shown above, refer to Figure 1.

Product Description

Marathon MR Rev. E2 04/2011 9

2.1 Theory of Operation for 2-Color Sensors

Two-color ratio technology makes possible accurate and repeatable temperature measurements that
are free from dependence on absolute radiated energy values. In use, a 2-color sensor determines
temperature from the ratio of the radiated energies in two separate wavelength bands (colors).

The benefits of 2-color sensors are that accurate measurements can be made under the following
conditions:

When the field of view to the target is partially blocked or obscured.
When the target is smaller than the sensor’s field of view.
When target emissivities are low or changing by the same factor in both wavelength bands.

Another benefit is that 2-color sensors measure closer to the highest temperature within the measured
spot (spatial peak picking) instead of an average temperature. A 2-color sensor can be mounted farther
away, even if the target does not fill the resulting spot size. The convenience is that you are not forced

to install the sensor at some specific distance based upon target size and the sensor’s optical

resolution.

2.1.1 Partially Obscured Targets

The radiated energy from a target is, in most cases, equally reduced when objects or atmospheric
materials block some portion of the optical field of view. It follows that the ratio of the energies is
unaffected, and thus the measured temperatures remain accurate. A 2-color sensor is better than a
1-color sensor in the following conditions:

Sighting paths are partially blocked (either intermittently or permanently).
Dirt, smoke, or steam is in the atmosphere between the sensor and target.
Measurements are made through items or areas that reduce emitted energy, such as grills,

screens, small openings, or channels.

Measurements are made through a viewing window that has unpredictable and changing

infrared transmission due to accumulating dirt and/or moisture on the window surface.

The sensor itself is subject to dirt and/or moisture accumulating on the lens surface.

1-color sensors see polluted atmosphere and dirty windows and lenses as a reduction in
energy and give much lower than actual temperature readings!

2.1.2 Targets Smaller Than Field of View

When a target is not large enough to fill the field of view, or if the target is moving within the field of
view, radiated energies are equally reduced, but the ratio of the energies is unaffected and measured
temperatures remain accurate. This remains true as long as the background temperature is much
lower than the target’s. The following examples show where 2-color sensors can be used when targets
are smaller than the field of view:

Measuring wire or rod — often too narrow for field of view or moving or vibrating

unpredictably. It is much easier to obtain accurate results because sighting is less critical with
two-color sensors.

Measuring molten glass streams — often narrow and difficult to sight consistently with

single-wavelength sensors.

Product Description

10 Rev. E2 04/2011 Marathon MR

2.1.3 Low or Changing Emissivities

If the emissivities in both wavelengths (colors) were the same, as they would be for any blackbody
(emissivity = 1.0) or greybody (emissivity < 1.0 but constant), then their ratio would be 1, and target
emissivity would not be an influence. However, in nature there is no such thing as a greybody. The
emissivity of all real objects changes with wavelength and temperature, at varying degrees, depending
on the material.

When emissivity is uncertain or changing, a 2-color sensor can be more accurate than a 1-color
instrument as long as the emissivity changes by the same factor in both wavelength bands. Note,
however, that accurate measurement results are dependent on the application and the type of material
being measured. To determine how to use 2-color sensors with your application when uncertain or
changing emissivities are a factor, please contact your sales representative.

Technical Data

Marathon MR Rev. E2 04/2011 11

3

3.1 Measurement Specifications

Temperature Range

MR1SA 600 to 1400°C (1112°F to 2552°F)
MR1SB 700 to 1800°C (1292°F to 3272°F)
MR1SC 1000 to 3000°C (1832°F to 5432°F)

Spectral Nominal Response 1.0 µm nominal (Si/Si layered detector)

Spectral Band Response

1-color band 0.75 to 1.1 μm
2-color band 0.75 to 1.1 μm, 0.95 to 1.1 μm

System Accuracy ±(0.5% Tmeas + 2°C), Tmeas in °C

with no attenuation

Repeatability ±0.3% full scale

Temperature Resolution ±1°C (±2°F) for display and RS485 interface

Analog Output Resolution

MR1SA, MR1SB 1°C or 1°F

MR1SC 1°C or 2°F

Response Time (95% Response) all models 10 ms for signal to reach 95% of final temperature

Temperature Coefficient All models 0.03% full scale change per 1°C change in ambient

temperature

Emissivity (1-color) 0.10 to 1.00, digitally adjustable in increments of 0.01

Slope (2-color) 0.850 to 1.150, digitally adjustable in increments of 0.001

Signal Processing Peak hold, averaging

Noise Equivalent Temperature all models 1°C peak to peak, target emissivity of 1.00,
(NET) unobscured target
3°C peak to peak, for all specified attenuation conditions

Peak Hold Range 0.1 to 299.9 s (300 s = )

Averaging Range 0.1 to 299.9 s (300 s = )

Warm Up Period 15 minutes

Figure 1, Figure 2, and Figure 3 show each sensor model’s percentage of allowed signal reduction at

all temperatures. Refer to these graphs to estimate what percentage of target area must be visible to
the sensor at temperatures below the minimum temperature (95% attenuation) as shown in Table 1.

Technical Data

12 Rev. E2 04/2011 Marathon MR

Figure 1: Model A Percentage of Allowed Signal Reduction

Figure 2: Model B Percentage of Allowed Signal Reduction

Model A – up to 95% allowed signal reduction

800°C (1472°F) to 1400°C (2552°F)

Attenuation Factor

Target Temperature

Maximum Allowed Signal Reduction [%]

Model B – up to 95% allowed signal reduction

950°C (1742°F) to 1800°C (3272°F)

Attenuation Factor

Target Temperature

Maximum Allowed Signal Reduction [%]

Technical Data

Marathon MR Rev. E2 04/2011 13

Figure 3: Model C Percentage of Allowed Signal Reduction

3.2 General Specifications

Display 7-segment LED display—shows temperature, slope, emissivity,

peak hold seconds, average seconds, and failsafe codes.

Individual LED’s indicate modes and active functions (e.g.,

2C/1C mode, slope, emissivity, peak hold, and average)

Environmental Rating IP65 (IEC 529, NEMA-4)
Ambient Temperature

without cooling 0 to 50°C (32°F to 122°F)
with air cooling 0 to 120°C (32°F to 250°F)
with water cooling 0 to 175°C (32°F to 350°F)
with ThermoJacket 0 to 315°C (32°F to 600°F)

Storage Temperature

Electronics Housing -20 to 70°C (-4°F to 158°F)

Relative Humidity 10 to 95%, not condensing at 22°C to 43°C (72°F to 110°F)

Electromagnetic Interference CE Emission Standard: EN50081-2

CE Immunity Standard: EN50082-2

Mechanical Shock

Electronics Housing MIL-STD-810D (IEC 68-2-27), 50 G, 11 msec duration, 3 axis

Vibrations

Electronics Housing MIL-STD-810D (IEC 68-2-6), 3 G, 11 to 200 Hz 3 axis

Thermal Shock none

Warm up Period 15 minutes

Weight

sensor 480 g (17 oz)

Attenuation Factor

Target Temperature

Maximum Allowed Signal Reduction [%]

Model C – up to 95% allowed signal reduction

1300°C (2372°F) to 3000°C (5432°F)

Technical Data

14 Rev. E2 04/2011 Marathon MR

with air/water-cooled housing 800 g (28 oz)

Fail-Safe Full or low scale, depending upon system failure, see section

10.2 Fail-Safe Operation, Seite 50.

3.3 Electrical Specifications

Power Supply 24 VDC ±20%, 500 mA (max 100 mV peak to peak of ripple)

Power Consumption max. 12 W

Outputs

Analog 0 - 20 mA, 4 - 20 mA, active output, 16 bit resolution

max current loop impedance: 500 Ω

Digital RS485 networkable to 32 sensors

Baud rate: 300, 1200, 2400, 9600, 19200, 38400 (default)
Data format: 8 bit, no parity, 1 stop bit,
Software selectable 4-wire, full-duplex non-multidrop, point-to­point or 2-wire half duplex multidrop

Relay Contacts max. 48 V, 300 mA, response time < 2 ms, (software

programmable)
Relay Contacts Type: SPDT contact closure

Input

External Reset TTL input, trigger for resetting peak hold

Figure 4: External Reset Wiring Diagram

3.4 Dimensions

The following illustrations show dimensions of a standard sensor, see Figure 5, a sensor with the
air/water-cooled housing option, see Figure 6, and the adjustable bracket.

Dimensions are listed for your installation convenience.

Sensor

Trigger

GND

Technical Data

Marathon MR Rev. E2 04/2011 15

Figure 5: Dimensions of Sensing Head

Figure 6: Sensing Head with Air/Water-Cooled Housing Option

Figure 7: Adjustable Bracket

Technical Data

16 Rev. E2 04/2011 Marathon MR

3.5 Optical Specifications

Optical Resolution D:S (assumes 95% energy at the focus point)

MR1SA 44:1

MR1SB 82:1

MR1SC 130:1

Because the sensor has variable focus, through-the-lens sighting, and parallax-free optics, it can be
mounted almost anywhere. SF (Standard Focus) models can be focused from 600 mm (24 in) to
infinity, and CF (Close Focus) models can be focused from 300 mm (12 in) to 600 mm (24 in). For
1-color temperature measurements make sure the target completely fills the measurement spot. The
spot size for any distance, when the unit is properly focused, can be figured by using the following
formula and Figure 8.

Divide the distance (D, in Figure 8) by your model’s D:S number. For example, if a model C unit (D:S =
130:1) is 2000 millimeters (80 inches) from the target, divide 2000 by 130 (80 by 130), which gives you a
target spot size of 15 mm (0.6 in). A model A unit (D:S = 44:1) at 2000 mm (80 in) would measure a
target spot of 45 mm (1.8 in). Divide 2000 by 44 (80 by 44).

Figure 8: Spot Size Chart

D:S is a ratio and applies to either metric or non-metric measurements!

D = Distance
S = Spot size

Technical Data

Marathon MR Rev. E2 04/2011 17

3.6 Scope of Delivery

The scope of delivery includes the following:

Marathon MR Documentation and Support CD
Adjustable mounting bracket (XXXTXXACAB) with mounting nut
End cap for display

The cable with the terminal block needs to be ordered separately!

Environment

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4

Sensor location and configuration depends on the application. Before deciding on a location, you need
to be aware of the ambient temperature of the location, the atmospheric quality of the location
(especially for 1-color temperature measurements), and the possible electromagnetic interference in
that location. If you plan to use air purging, you need to have an air connection available. Also, wiring
and conduit runs must be considered, including computer wiring and connections, if used. The
following subsections cover topics to consider before you install the sensor.

4.1 Ambient Temperature

The sensing head is designed to operate in ambient temperatures between 0°C (32°F) and 50°C
(122°F). The internal ambient temperature can vary from 10°C (50°F) to 68°C (154°F). Internal
temperatures outside this range will cause a failsafe error. In ambient conditions above 50°C (122°F),
an optional air/water-cooled housing is available to extend the operating range to 120°C (250°F) with
air cooling, or 175°C (350°F) with water cooling. When using the water cooled housing, it is strongly
recommended to also use the air purge collar to avoid condensation on the lens. In ambient conditions
up to 315°C (600°F), the ThermoJacket accessory should be used.

When using air or water cooling and air purging, make sure air and water supplies are installed
before proceeding with the sensor installation.

Water and air temperatures for cooling should be 15-30°C (60-86°F) for best performance. Chilled
water or air below 10°C (50°F) is not recommended. For air purging or air cooling, clean (filtered) or
“instrument” air is recommended.

4.2 Atmospheric Quality

Smoke, fumes, dust, and other contaminants in the air, as well as a dirty lens are generally not a
problem when using the 2-color mode (as long as the attenuation is equal in both spectral bands).
However, if the lens gets too dirty, it cannot detect enough infrared energy to measure accurately, and
the instrument will indicate a failure. It is good practice to always keep the lens clean. The Air Purge
Collar helps keep contaminants from building up on the lens.

If you use air purging, make sure an air supply with the correct air pressure is installed before
proceeding with the sensor installation.

4.3 Electrical Interference

To minimize electrical or electromagnetic interference or “noise” be aware of the following:

Mount the electronics enclosure as far away as possible from potential sources of electrical

interference such as motorized equipment producing large step load changes.

Use shielded wire for all input and output connections.
Make sure the shield wire from the electronics to terminal block cable is earth grounded.
For additional protection, use conduit for the external connections. Solid conduit is better than

flexible conduit in high noise environments.

Do not run AC power for other equipment in the same conduit.