Ohmic instruments AMM-15 User manual

1
AMM-15 Manual
AIR-LINE MOISTURE MONITOR
Model AMM-15
Phone [phone]
Toll Free(800) 626-7713
Fax [phone]
www.ohmicinstruments.com
Sales: [e-mail]
Service: [e-mail]
Ohmic Instruments
3081 Elm Point Industrial Drive
St. Charles, MO 63301 USA
SF-SLS-546 (B)

2
© Ohmic Instruments
2021
All rights reserved. This manual may not be reproduced in complete form
without written permission of Ohmic Instruments. Individual pages may be
copied as required by the original purchaser of the instrument. Information
contained in this manual is believed to be accurate and reliable; however, no
responsibility is assumed by Ohmic Instruments for its use. Ohmic reserves the
right to supply its instruments with design changes and/or component
substitutions that may not be documented in this manual.

3
Contents
Storage Recommendations…………………………………………………...4
Introduction................................................................................................5
Sample Modes / Connecting Information ..................................................6
Operating Instructions ...............................................................................8
RS-232 Interface .......................................................................................8
Logging and Data Uploading...................................................................10
Changing Settings Using the Interior DIP Switch....................................10
Summary of Computer Commands.………………………………………. 11
Notes on Communication and Command Structure................................12
Analog Output Table ...............................................................................13
General Specifications ............................................................................14
Warranty ..................................................................................................15

4
* Storage recommendations:
To prevent damage to the unit or changes to the
sensor elements the unit should be stored at 0 to 125
Deg. F. at less than 90 % RH. Long term storage of
the AMM-15 out of these conditions is not
recommended by Ohmic Instruments.
We also recommend removing the batteries if the
unit will not be used for an extended period.

5
Ohmic Model AMM-15 Air-line
Moisture Monitor is a portable hand
-held instrument designed to accu-
rately monitor the dew point and dry
-bulb temperatures in compressed
air lines as well as low pressure
systems. The unit is Microproces-
sor-based and is powered by four
size-AA alkaline batteries or by the
enclosed AC Adapter. Four front-
panel keypad switches provide
power on, power off, choice of
Dewpoint / dry-bulb temperature
display, and choice of °F / °C units.
The display is a 3-½ digit LCD with
0.5" digit height. The AMM-15 de-
termines the dew point temperature
from measurements of humidity
and dry-bulb temperature of the
sample air from the system under
test. Dew point is then calculated
from these measurements using
pre-programmed psychrometric
equations and is fully compensated
for variations in sample dry-bulb
temperature. Connection to system
is accomplished via plastic quick
disconnects provided with the unit.
Model AMM-15 is an ideal choice
for personnel involved in operating,
maintaining, or inspecting com-
pressed air systems in medical,
commercial, and industrial facilities.
Features of the AMM-15 include:
• Dew point measurement range
from -40 to +80 °F
• Durable case with sealed mem-
brane keypad and 3-½ digit dis-
play
• Sample compressed air or low
pressure systems
• Analog and RS-232 outputs for
data transmission
• 32-Kbytes Data Logger memory
INTRODUCTION

6
The AMM-15 is designed for use with
both compressed and low pressure
air systems, and can accurately
measure conditions in air lines oper-
ating at pressures from 0 to 120 psi.
Two ports are provided for flexibility:
free flow mode can be used when the
pressure or flow-rate is very low; al-
ternatively, for systems with line pres-
sures above 5 psi, an 0.008" orifice is
provided to maintain controlled flow
rates for highest accuracy.
Monitoring Plastic Resin Dryers,
Ovens, and Low Pressure Vessels
In low pressure applications
(pressure less than 5 psig), use the
free-flow mode. This is done by con-
necting the inlet port to the sample air
source using the quick connect fitting
provided, making sure that the filter is
connected between the unit and the
sampled air source. A suggested
hook-up diagram of this is on the fol-
lowing page. If there is sufficient pres-
sure and flow, the second sample
port can be exhausted to ambient or
reconnected to the sample source at
a lower pressure point, providing
closed-loop monitoring. If necessary
where the source pressure is insuffi-
cient to provide positive flow, a vacu-
um pump can be connected to the
second sample port to help draw a
sample.
Monitoring Compressed Air or
Pressurized Vessels
In compressed air applications
(above 5 psi), the dew point meas-
urements are made at line, rather
than atmospheric pressure, eliminat-
ing the need to calculate pressure
dew points. The air is vented to ambi-
ent through a back pressure orifice
installed on the exhaust. Install the
exhaust orifice, provided with the
AMM-15, in the outlet port. The
0.008" orifice restricts the exhaust
flow with a negligible pressure loss to
maintain controlled flow rates for
highest accuracy. Connect the inlet
port to the air source following the
diagram on the next page. Be
careful not to connect the AMM-15
to line pressure in free-flow mode;
the resulting high flow rate will
damage the internal sensors.
Note on High Temperature
Applications
For temperatures up to 140°F, the
poly tubing supplied with the AMM-15
is sufficient. Air sources above 140°F
and up to 550°F can safely be meas-
ured using a 6-foot length of ¼" O.D.
copper tubing to dissipate the excess
heat. Cooling the sample will not
change the dew point, but will protect
the AMM-15 from damage.
SAMPLE MODES / CONNECTING INFORMATION

7
AMM-15 CONNECTIONS
IMPORTANT
THE OUTLET ORIFICE
MUST BE USED WHEN
WORKING WITH 5 PSI
OR GREATER.
This orifice maintains the
test cell at line pressure; if
the orifice is omitted, false
readings will result.
Filter
Brass Orifice
Assembly
Outlet
Inlet
Hose barb to
Quick Connect
¼” OD Hard
Tubing
Metal Quick
Connect
Metal Quick
Connect
Remaining ¼”
OD Hard Tubing

8
OPERATING INSTRUCTIONS
1. Make sure the alkaline batteries
have sufficient power. The display
will show the low battery symbol if
the batteries are inadequate. If the
instrument has not been used for
a period of time, the batteries
should be checked and replaced if
necessary. If desired, the AMM-15
can be operated from the AC
Adapter (it does not charge the
batteries). As with all such equip-
ment, if the unit is not to be used
for an extended period, the batter-
ies should be removed.
2. Purge the air line to be tested of
any water, oil, or other foreign
matter. The sensors are suscepti-
ble to contamination and damage
from impurities such as water, oil,
dust, chemicals, etc. THE PRO-
VIDED FILTER MUST BE BE-
TWEEN THE AMM-15 AND THE
SYSTEM BEING SAMPLED
FROM. FAILURE TO USE THE
FILTER VOIDS THE WARRAN-
TY. OHMIC INSTRUMENTS IS
NOT RESPONSIBLE FOR MIS-
USE OR NEGLECT OF THE
UNIT.
3. Connect the AMM-15 to the air
line following the recommenda-
tions on the Sample Modes /
Connecting Information page.
[AIR LINE PRESSURE IS NOT
TO EXCEED 120 PSI]
4. Press the ON button. The AMM-
15 always displays Dewpoint on
power up. The DP / DB selector
button will change the displayed
parameter from Dewpoint to Dry
Bulb Temperature. The display
will show a "down" arrow when
displaying Dewpoint and an "up"
arrow when displaying Dry Bulb
Temperature. The °F / °C selector
button will change the displayed
parameter from degrees Fahren-
heit to degrees Celsius.
5. Allow sufficient time for the read-
ings to stabilize. Normal stabiliza-
tion will occur within 1 to 1-½
minutes. Very low readings, less
than -10°F DP, will take up to 10
or 15 minutes for stabilization.
Analog Output
The AMM-15 provides an analog
output of 0-1 VDC (from –55 to +95°
F Dew Point). Use the enclosed 2-
wire plug adapter, and connect a
voltmeter to the wires: Red/white to
positive (+) and black/white to nega-
tive (-). Plug the adapter into the jack
marked Analog Out, and see the
table on Page 13 for values.
RS-232 INTERFACE– Connect-
ing the AMM-15 to your Comput-
er
Connecting to a serial port The
AMM-15 can be plugged into any 9-
pin PC serial (COM) port using a 9-
pin serial cable, available from most
computer stores. If your computer
has a 25-pin COM port, 25-pin to 9-
pin serial adapters are also available
from most computer stores and can
be used with the cable [Serial data is
transmitted using Pin 5 (ground), Pin
3 (transmit), and Pin 2 (receive)].
Some computer COM ports and seri-
al adapters are not fully implemented
(not all pins are used). If the AMM-15
is connected to a partially implement-
ed serial port, functions may be errat-
ic or the unit may fail to communi-
cate. Please consult the owner’s
manual for your computer if this oc-
curs. Set up your communications
program as described on the next
page.

9
Connecting to a USB port If your
computer has USB ports you can get
an optional RS-232 to USB adapter
from Ohmic. Ohmic recommends
using an RS-232 to USB adapter only
with Windows XP© and Windows
Vista©. Connect the AMM-15 using
the RS-232 adapter and RS-232 to
USB adapter. Turn on your computer.
When your computer recognizes the
device click OK and follow the instruc-
tions for installing the driver software.
Set up your communications program
as described below.
Communications Programs
The AMM-15 transmits data via its RS
-232 output as soon as it is powered
up. In order to receive the data, a
communications (or terminal) program
must be running on your computer.
We recommend Tera Term; it is easy
to use, free, and available for down-
load from www.download.cnet.com.
When you reach that page, type “Tera
Term” in the Search box; you will then
be able to download the installation
program. Then:
1. Install the program and run it.
2. A New Connection window will
open. Click the “Serial” button,
then select the COM port you will
be using, and click OK.
3. Tera Term should now be ready to
receive data from the AMM-15.
Make sure they are connected via
the adapter cable, and power up
the AMM-15.
4. Text will be displayed indicating
the version of the embedded pro-
gram. The computer will then dis-
play four numbers, as indicated
below:
(Date) (Time) (Dew Point) (Temp.)
mm/dd/yy hh/mm/ss xx.x xxx.x
New readings will be displayed
every few seconds and are in a
comma delimited format that can
be copied and pasted into a
spreadsheet program, if desired.
If readings are not displayed, turn the
AMM-15 off, and in Tera Term click
on Setup in the menu bar, then se-
lect Serial Port. This will open a win-
dow where you can check several
parameters:
• Port: Try another port until you
find the right one.
• Baud rate: Should be 9600.
• Data: 8 bit
• Parity: None
• Stop: 1 bit
• Flow Control: Off
Once you get a working display you
may want to save your settings. Re-
fer to Tera Term’s help file for infor-
mation on this and other functions.
Other communications programs can
also be used; some older versions of
Windows include one called Hyper-
Terminal. Refer to its help file for
information on using it and applying
the parameters above.

10
LOGGING AND DATA
UPLOADING
The AMM-15 can be set to log data at
four fixed intervals of 5, 10, 30, and
60 seconds. The factory preset de-
fault is 60 seconds, but this can be
changed using the DIP switch and
chart below.
A maximum of 2860 Dew Point and
Temperature readings can be stored.
However, once the memory logging
space has been filled, a wrap feature
of the memory storing causes the
oldest data to be overwritten. Thus,
when the memory is full, the logger
will hold a "sliding window" spanning
the 2860 readings.
Uploading the logged data can be
done at any point. The stored read-
ings are transmitted chronologically,
each line of the display correspond-
ing to one scan of the sensors. For a
full logger memory of 2860 readings,
uploading takes approximately three
minutes. Note, however, that a slow
scrolling speed of the terminal screen
might stretch this interval to about
four and a half minutes.
Uploading will not clear the logger
memory, which makes repeated up-
loading of the same data possible.
Data will be stored in the nonvolatile
memory incorporated into the AMM-
15, without having power applied to
the unit, for as long as ten years.
CHANGING SETTINGS USING THE
INTERIOR DIP SWITCH
S1 is a 4-pole DIP switch that can be
accessed by removing the 4 screws
from the back of the unit and carefully
opening the case. When reassem-
bling the AMM-15 be careful not to
pinch any wires.
The log rate and baud rate can be
adjusted using switches 1, 2, and 3.
Caution: Switch #4 locks the calibra-
tion points for the AMM-15 and
should be left in the ON position.
Each AMM-15 ships with DIP switches 1, 2, and 3 off, and 4 on.
S1
1 2 3 4
OFF
OF F
O FF
ON ON
L OC K E D = O N
ON
ON
120 0 = O N
L O G R AT E B AU D R AT E L O CK O U T
4
U NLO C K ED = O F F
60
30
1 2 3
se c.
O FF O FF
960 0 = O FF
10
5

11
SUMMARY OF COMPUTER COMMANDS
The following is a list of commands accepted by the AMM-15. Make sure you
read through the notes on Page 10 before attempting to change any of the
settings. Each command should be followed by pressing the Enter key.
Toggles display of readings On / Off. Logging
always comes on when the unit is powered up
using the keypad ON button.
Transmit current settings of parameters.
Change computer display to Celsius.
Change computer display to Fahrenheit.
Set date and time for real time clock:
MM = month (01--12)
DD = day (01--31)
YY = year (00--99)
hh = hours (00--23)
mm = minutes (00--59)
ss = seconds (00--59)
Clear stored data.
Upload stored data. Readings, including a time
stamp, are transmitted in chronological order,
one line corresponding to one scan of the sen-
sors.
Halt the uploading of data. This command can be
used only when uploading is in progress.
C
S
SC
SF
TMM DD YY hh mm ss
E9090
U
H
When halted, only two commands are accepted:
Q
U
Terminate the uploading in progress and resume
the measurement and logging functions. This
command can be used only following the Halt
command (H).
Resume uploading data. This command can be
used only following the Halt command (H).
See the note on the next page if the computer does not display what you are
typing.

12
If the computer screen does not
display what you are typing, go to
the menu bar in Tera Term, click
on Setup, select Terminal, and
checkmark the “Local Echo” box.
1. All alpha characters are in UP-
PER CASE (turn on your Caps
Lock key).
2. All transmissions from the AMM
-15 to the host computer end
with a Carriage Return (CR)
followed by a Line Feed (LF),
except for uploads, which end
with just a (CR).
3. An invalid command, followed
by pressing the Enter key, gen-
erates the transmission of a “?”
character.
4. The data transmission format
is:
(TAB)##.#,(TAB)###.#(CR)(LF)
where the numbers (#) corre-
spond to Dew Point and Tem-
perature respectively.
Each scan of the sensors is
preceded by a time stamp in
the form:
MM/DD/YY hh:mm:ss
For example, 04/10/13 16:30:05
is April 10, 2013 at 4:30:05 PM.
5. The time interval between com-
mands should be at least 1 sec-
ond.
6. During the execution of a com-
mand, the scanning of the sen-
sors will be suspended. This
fact should be taken into con-
sideration, mainly in connection
with the uploading command.
REPLACEMENT PARTS
Inline Filter.............................................................................................. #5355
¼" OD Polypropylene Tubing (6-foot) ...........................................ST-AMM-15
If you need additional help for your particular application, contact Ohmic at
[phone], or e-mail us at s[email protected].
NOTES ON COMMUNICATION AND COMMAND STRUCTURE

13
AMM-15 ANALOG OUTPUT TABLE
NOTE: Output is calibrated only in the range of –40°F to +80°F
and –40°C to +27°C.
DP Vout (mV) DP Vout (mV) DP Vout (mV) DP Vout (mV)
-55 0.00 -17 253.33 21 506.67 59 760.00
-54 6.67 -16 260.00 22 513.33 60 766.67
-53 13.33 -15 266.67 23 520.00 61 773.33
-52 20.00 -14 273.33 24 526.67 62 780.00
-51 26.67 -13 280.00 25 533.33 63 786.67
-50 33.33 -12 286.67 26 540.00 64 793.33
-49 40.00 -11 293.33 27 546.67 65 800.00
-48 46.67 -10 300.00 28 553.33 66 806.67
-47 53.33 -9306.67 29 560.00 67 813.33
-46 60.00 -8313.33 30 566.67 68 820.00
-45 66.67 -7320.00 31 573.33 69 826.67
-44 73.33 -6326.67 32 580.00 70 833.33
-43 80.00 -5333.33 33 586.67 71 840.00
-42 86.67 -4340.00 34 593.33 72 846.67
-41 93.33 -3346.67 35 600.00 73 853.33
-40 100.00 -2353.33 36 606.67 74 860.00
-39 106.67 -1360.00 37 613.33 75 866.67
-38 113.33 0366.67 38 620.00 76 873.33
-37 120.00 1373.33 39 626.67 77 880.00
-36 126.67 2380.00 40 633.33 78 886.67
-35 133.33 3386.67 41 640.00 79 893.33
-34 140.00 4393.33 42 646.67 80 900.00
-33 146.67 5400.00 43 653.33 81 906.67
-32 153.33 6406.67 44 660.00 82 913.33
-31 160.00 7413.33 45 666.67 83 920.00
-30 166.67 8420.00 46 673.33 84 926.67
-29 173.33 9426.67 47 680.00 85 933.33
-28 180.00 10 433.33 48 686.67 86 940.00
-27 186.67 11 440.00 49 693.33 87 946.67
-26 193.33 12 446.67 50 700.00 88 953.33
-25 200.00 13 453.33 51 706.67 89 960.00
-24 206.67 14 460.00 52 713.33 90 966.67
-23 213.33 15 466.67 53 720.00 91 973.33
-22 220.00 16 473.33 54 726.67 92 980.00
-21 226.67 17 480.00 55 733.33 93 986.67
-20 233.33 18 486.67 56 740.00 94 993.33
-19 240.00 19 493.33 57 746.67 95 1000.00
-18 246.67 20 500.00 58 753.33

14
GENERAL SPECIFICATIONS
AIR-LINE MOISTURE MONITOR - Model AMM-15
ELECTRICAL
Water Vapor Sensor: HC-610 (Thin Film Polymer)
Temperature Sensor: 10K NTC Thermistor
Dewpoint Range: -40 to +80 F
Dewpoint Accuracy: ±4 F from -40 to +20; ±2 F from +20 to +80
Dry-Bulb Range: 0 to 140 F
Dry-Bulb Accuracy: ±2 F
Average Response Time: 10 Seconds / 63% Step
Max. Inlet Temperature: 140 F 550F with Heat Sink Tubing
Maximum Line Pressure: 120 PSIG
Display: 3-1/2 Digit LCD, 0.5" Character Height
Power: 4-AA Alkaline Batteries
Microprocessor: Philips 80C552
Clock Rate: 3.6864 MHz
COMMUNICATIONS
Type: RS-232C
Rate: 9600 Baud
Parity: None
Data Bits: 8
Stop Bits: 1
Flow Control: Off
Format: ASCII
Connector: DB9 Female
PHYSICAL
Housing: High Impact ABS Plastic
Size: 8.25” x 4.0” x 1.6” (LWH)
Weight: 24 Ounces

15
Not withstanding any provision of any agreement
the following warranty is exclusive.
Ohmic Instruments warrants each instrument it
manufactures to be free from defects in material
and workmanship under normal use and service for
the period of 1-year from date of purchase. This
warranty extends only to the original purchaser.
This warranty shall not apply to fuses or any prod-
uct or parts which have been subjected to misuse,
neglect, accident, or abnormal conditions of opera-
tion.
In the event of failure of a product covered by this
warranty, Ohmic Instruments will repair and recali-
brate an instrument returned within 1 year of the
original purchase: provided the warrantor's exami-
nation discloses to its satisfaction that the product
was defective. The warrantor may, at its option,
replace the product in lieu of repair. With regard to
any instrument returned within 1 year of the original
purchase, said repairs or replacement will be made
without charge. If the failure has been caused by
misuse, neglect, accident, or abnormal conditions
of operations, repairs will be billed at a nominal
cost. In such 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 MERCHANTABIL-
ITY, FITNESS, OR ADEQUACY FOR ANY PAR-
TICULAR PURPOSE OR USE. OHMIC INSTRU-
MENTS SHALL NOT BE LIABLE FOR ANY SPE-
CIAL, INCIDENTAL, OR CONSEQUENTIAL DAM-
AGES, WHETHER IN CONTRACT, TORT, OR
OTHERWISE.
If any failure occurs, the following steps should
be taken:
1. Notify Ohmic Instruments giving full details of the
difficulty, and include the model, type, and serial
numbers (where applicable). On receipt of this
information, service data, or shipping instruc-
tions will be forwarded to you.
2. On receipt of shipping instructions, forward the
instrument, transportation prepaid. Repairs will
be made and the instrument returned, transpor-
tation prepaid.
SHIPPING TO MANUFACTURER FOR REPAIR
OR ADJUSTMENT
All shipments of Ohmic Instruments products
should be made via United Parcel Service or "Best
Way" prepaid. The instrument should be shipped in
the original packing carton, or if it is not available,
use any suitable container that is rigid and of ade-
quate size. If a substitute container is used, the
instrument should be wrapped in paper and sur-
rounded with at least four inches of excelsior or
similar shock absorbing material.
CLAIM FOR DAMAGE IN SHIPMENT TO ORIGI-
NAL PURCHASER
The instrument should be thoroughly inspected
immediately upon delivery to purchaser. All material
in the shipping container should be checked
against the enclosed packing list. The manufacturer
will not be responsible for shortages against the
packing sheet unless notified immediately. If the
instrument is damaged in any way, a claim should
be filed with the carrier immediately. (To obtain a
quotation to repair shipment damage, contact
Ohmic Instruments.) Final claim and negotiations
with the carrier must be completed by the custom-
er.
Ohmic Instruments will be pleased to answer all
application or use questions, which will enhance
your use of this instrument. Please address your
requests or correspondence to:
Ohmic Instruments
3081 elm Point Industrial Drive
St. Charles, MO 63301 USA
ATTN: Technical Support. Or call Ohmic Tech-
nical Support at 410-820-5111.
All rights reserved. This manual may not be repro-
duced in full or in part without written permission of
Ohmic Instruments Company. Information con-
tained within this manual is believed to be accurate
and reliable. However, Ohmic Instruments Compa-
ny assumes no liability for its use. Ohmic Instru-
ments Company reserves the right to supply its
instruments with design changes and/or component
substitutions that may not be documented in this
manual. Contact our engineering department for
information on equipment revisions not covered in
this manual.
WARRANTY
Phone [phone]
Toll Free(800) 626-7713
Fax [phone]
www.ohmicinstruments.com
Sales: [e-mail]
Service: [e-mail]

16