How to use a photogate for frequency measurement using a NI USB-6211

Hello, I am extremely new to LabView and am having trouble using the counter feature (or if this is even what I should be doing). I am trying to use a photogate as a frequency counter when a voltage spike is created by blocking the sensor. This will then be put into RPM and used to evaluate a small motor dyno I am creating. If anyone has any help or previous vi's they dont mind sharing it would be greatly appreciated. The photogate specifications are for an optek opb930l55. Thanks

Configuring a counter input task will be a little different depending on the type of DAQ card that you are using to read the digital pulses. You just need to wire the voltage from the photogate to one of the counter pins on the card. Then follow one of the many examples for measuring the frequency of pulses. If your card allows it, I would suggest choosing the Counter Input >> Frequency measurement from the DAQmx Create Channel VI. If you have questions about how to do this with your specific DAQ device, please provide more information
Zach C.
Field Engineer
Greater Los Angeles

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6602: How to use 8 counters simultaneously in C++ using traditional Daq for frequency measurement

Hi Everybody;
I'm new to Ni-DAQ cards and working on NI PCI-6602 Card in Borland C++, I should use Traditional DAQ for my project. Now I want to use all the 8 counters simultaneously for frequency measurement.
1.Where should I connect my External signal, to source or gate, at present I have connected to source.
2. How to set parameters and start the counters simultaneously, what are the parameters to be set for frequency measurement.
3.How to start counting.(parameter settings)
4.Should I set any PFI Lines or by default are they set to counters.
status = GPCTR_Set_Application (1, gpctrNum, ND_SIMPLE_EVENT_CNT)
status = GPCTR_Change_Parameter (1, gpctrNum, paramID, paramValue)
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what is the paramID in my case, Clear and appropriate answers would be very helpful and thanks in advance.
Message Edited by Pavan K on 07-11-2009 12:38 AM

I have made a program with LabVIEW 5.1 based on NI 6602, in which four counters were used.
Counter 3 is used to generate pulses, which are directed to the gates of counter 0, 1 and 2.
The source terminals of counter 0,1 and 2 receive pulses, individually, to count how many pulses appear during the time interval of each gate pulse.
The results are stored in a data file.
In order to test its performance, only one signal of ramdom pulses is sent to counter 0,1 and 2.
But I find that at the beginning the counts for the three counters are the same, but the following counts are totally different!
What's wrong? And how to solve such a problem? Does it have something related with synchronization?
Thank you very much!

Frequency measurement using Labview 8 and Fieldpoint FP-CTR-502 - wind speed measure

All the information regarding this kind of application seems to be outdated, I did not find no solution or example to construct frequency measurement VIs using Labview 8
The examples at "NI Discussion Forums :
Most Active Hardware Boards :
FieldPoint Family :
Low-Frequency measurements using counter/timer" is very strange and so far the steps given seems to be usefull only do old Fieldpoint Explorer.
I was trying to find a way to learn how to make an anemometer send its signal to a FP-CTR-502 but I have no sucess.
I am realy very new on this Labview stuff, any help would be welcome.

(similar thread here)
Message Edité par Mathieu R. le 12-23-2005 02:28 PM
.mrLeft{float:left} .mrInfo{border-left:solid 1px #989898;font-size:x-small;color:#989898}
Mathieu R.
  CTD - Certified TestStand Developer / Développeur TestStand Certifié
  CLAD - Certified LabVIEW Associate Developer

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Low Frequency Measurements using counter timers

I am trying to measure multiple speeds using FP-CTR-502 modules. I am having a resolution problem. Looking at the post at the following URL (http://forums.ni.com/ni/board/message?board.id=110&message.id=3601&query.id=42252#M3601) looks like exactly what I need to do, but I'm not sure how to program this. Does anyone have any example code to get me headed in the right direction?

Hi Tcrower,
Here is the example that Carl L. was describing in his forum post along with his instructions. Also, there are thorough instructions for using the program in the front panel as well as in File >> VI Properties >> Documentation.
You can measure frequency in two ways using a counter.
1) Measure the time it takes for a set number of pulses to pass or,
2) Count the number of pulses that pass in a set amount of time.
For low-frequency signals it is best to measure the time duration of a set number of pulses. If we tried to calculate the number of pulses that passed in a set amount of time, we would need a long gate period to get accurate results.
The drawback of measuring the amount of time it takes for a set number of pulses to pass is that the sample period varies with the frequency of the signal.
To accurately measure low frequencies with a CTR module, select two counter channels, one output channel, and one gate input channel. Count Input 0 counts the pulses of the signal that we are measuring. The output of the counter is set to high for x pulses and low for x pulses, which is used as the gate of Count Input 1. The source of Count Input 1 is the internal clock reference (the example can be modified to use an external clock reference). During the high phase of Count Input 0, Count Input 1 counts the pulses of the clock reference.
During the low phase, we read channel 1 and reset the counter.
For example, if the output of Count Input 0 is set to high for 4 pulses and the signal has a frequency of 20 Hz, the output of Count Input 0 is high for 200 ms. During the high phase, we will count 200 counts if we are using the 1 kHz internal clock reference. So to calculate the frequency, we have F = #pulses/duration = timebase * terminal count/counts = 1000 Hz * 4 terminal counts/200 counts = 20 Hz.
Regards,
Hal L.
Attachments:
Low_Frequency_Measurement_(CTR).zip ‏77 KB

Low-Frequency measurements using counter/timer

I am trying to measure speed, and am using the FP-502 counter timer module to count the pulses from my sensor. The field point example that uses a fixed width gate pulse will not work for my appliation because I need a gate pulse so big that it updates way to slow.
Does anybody have any sugestions on how to measure a low frequency signal using a counter/timer?
Thanks
Dan

Hello guys
Thanks for all your sugestions I have the final results. I got it to work but I would like to add some comments for anybody who is trying to attempt this.
Triggeing on the gate is a must for low frequency measurements. I used the divide by sugestion however using a factor of 3 only gets you about 60 Hz after that you can't sample fast enough. My application required me to measure from 0 to 150 Hz. I added a "gear shifter" routine where the terminal count was set to 3 on frequencies lower then 45 Hz and 15 for frequiencies greater than 45 Hz. Using a terminal count of 15 for all measurements made the udate rate on really low frequencies way to slow i.e. .5 seconds for 20Hz (check the math on this).
I a
lso needed to cascade the counters. At low frequencies the count went higher than 6550. Using the previos channel function of the fieldpoint module enable me to get 32 bit worth of terminal count data.
Finally I needed to add a timeout condition for 0 Hz. If there are no pulses coming from the senser the program displays the last value read. That won't be 0. So I added a time out routine that if I didn't see a pule in a certian amout of time, output 0 and reset the gate count.
Thank you for you help you relly saved me. I hope my comments made sense.
Dan

Constructing Calculated Measures in MDX for different measures using same columns in a fact table

Hello,
i have a fact table with 2 columns corresponding to dimensions Dim1, Dim2. In the same table i have 4 other columns Value_Type(int), INT_VALUE(int), FLOAT_VALUE(float), TEXT_VALUE(string). There are a number of measures which are identified by Value_Type and
depending on their nature could be written in one of the 3 columns (INT_VALUE(int), FLOAT_VALUE(float), TEXT_VALUE(string)) Let's say Measure1 with Measure_Type=1 is age, 2 is account balance and 3 is Name for clarity. There could be other measure types that
use these 3 same columns for data. So the sample fact table looks like this
Dim1 Dim2 Measure_Type INT_VALUE FLOAT_VALUE TEXT_VALUE
10 10 1 25
10 10 2 2000,34
10 10 3 John
10 20 1 28
10 20 2 3490,23
10 20 3 Frank
My task is to write an MDX query for each Dim1, Dim2 combination which returns all 3 measures in the same row. The idea is to construct a calculated member for each Measure that returns value from the right field. For example for Measure1 we take INT_VALUE
with measure_type=1. The problem is i don't know how to construct MDX query for these calculated members. Can you please help me?
So my final goal is to write an MDX query that returns all measures in one row for each set of Dim1, Dim2
SELECT [Measure1], [Measure2], [Measure3] ON COLUMNS,
NON EMPTY [Dim1].[Dim1].[Dim1].Members*[Dim2].[Dim2].[Dim2].Members ON ROWS
FROM [Cube]
Dim1 Dim2 Measure1 Measure2 Measure3
10 10 25 2000,34 John
10 20 28 3490,23 Frank

Hi Kosmipt,
I would combine the "INT_VALUE", "FLOAT_VALUE" and "TEXT_VALUE" columns into one with STRING data type for the fact table. And there should be one dimension to store the Measure_Type informations. Then in cube, you can write MDX scope for every one of
"Measure_Type" dimension members. For example,
scope(
            [Measures].[M]
    [DimMType].[MType].&[1]= CINT([Measures].[M]);
end scope;
Once the cube is built by the above way, you can write MDX like something like the following to achieve your purpose.
WITH member [Measures].[Measure1] AS ([DimMType].[MType].&[1],[Measures].[M])
         member [Measures].[Measure2] AS ([DimMType].[MType].&[2],[Measures].[M])
         member [Measures].[Measure3] AS ([DimMType].[MType].&[3],[Measures].[M])
thanks,
Jerry

How to select a row for update values, Using CTEs or suitable method

HI All,
I have a table as claim_data as below.
claim_id
amount         change_monthkey
         created_monthkey
         ord
54511
300            201304
         201304
          1
54511
0              201305
         201304
          2
120301
250            201502
         201502
          1
120624
150            201502
         201502
          1
120624
0              201503
              201502
          2
I want to isolate rows which appear in the table and do a update using below query ( This query is already in a procedure, so I just looking for a suitable way to modify it to support my task )
In the above e.g. ONLY row containing claim_id = 120301 needs to update (amount as updated_amount)
I use following query, but it update other rows as well, I want a suitable query only to capture rows of nature claim_id = 120301 and do this update? Is there any functions that I could use to facilitate my task??
select
     a.claim_id
   , a.Created_MonthKey
   , a.Change_MonthKey
   , a.amount - ISNULL(b.amount,0.00) as amount_movement
   ,a.amount as updated_amount   --- >> I need help here??
   FROM claim_data a
LEFT JOIN claim_data b
   ON a.claim_id = b.claim_id
   AND b.Ord = a.Ord - 1
Thanks
Mira

Please follow basic Netiquette and post the DDL we need to answer this. Follow industry and ANSI/ISO standards in your datC1. You should follow ISO-11179 rules for naming data elements. You do not know this IT standard.
You should follow ISO-8601 rules for displaying temporal datC1. We need to know the data types, keys and constraints on the table. Avoid dialect in favor of ANSI/ISO Standard SQL.
And you need to read and download the PDF for:
https://www.simple-talk.com/books/sql-books/119-sql-code-smells/
>> I have a table AS claim_data AS below. <<
Thanks to your lack of netiquette, we have no name, no DDL, no keys and have to re-type the raw data into SQL, guess at everything! Does your boss treat you with the same contempt?
Think about how silly “_data” is AS an attribute property! What tables do you have without an data in them? You had to give this meta-data in 1970's operating systems, FORTRAN compilers, etc. but we do not do this today. I see you use “A”, “B”, etc for table
aliases This is the name of the disk or tape drive in a 1970 computer! In SQL we use helpful, meaningful table aliases so code is easier to maintain. I see you also use the old punch card trick of putting a comma at the front of each line of code.
The column named “ord” is a mathematical fiction for ordinal sets. I think you meant to use it as a non-relational sequential number to let you keep writing 1970's COBOL is T-SQL. We have not used the old Sybase ISNULL() since we got COALESCE() in SQL-92. They
are actually different.
First, let's post what you should have posted if you followed forum rules:
CREATE TABLE Claims
(claim_id CHAR(5) NOT NULL,
claim_amount DECIMAL (8,2) NOT NULL
CHECK (claim_amount >= 0.00),
change_month_name CHAR(10) NOT NULL
REFERENCES Month_Period(month_name),
creation_month_name CHAR(10) NOT NULL
REFERENCES Month_Period(month_name),
ord INTEGER NOT NULL, -- NO!! Awful design!
PRIMARY KEY (claim_id, ord)); --required by definition
Since SQL is a database language, we prefer to do look ups and not calculations. They can be optimized while temporal math messes up optimization. A useful idiom is a report period calendar that everyone uses so there is no way to get disagreements in the DML.
The report period table gives a name to a range of dates that is common to the entire enterprise.
CREATE TABLE Month_Periods
(month_name CHAR(10) NOT NULL PRIMARY KEY
CHECK (month_name LIKE '[12][0-9][0-9][0-9]-[01][0-9]-00'),
month_start_date DATE NOT NULL,
month_end_date DATE NOT NULL,
CONSTRAINT date_ordering
CHECK (month_start_date <= month_end_date),
etc);
These report periods can overlap or have gaps. I like the MySQL convention of using double zeroes for months and years, That is 'yyyy-mm-00' for a month within a year and 'yyyy-00-00' for the whole year. The advantages are that it will sort with the ISO-8601
data format required by Standard SQL and it is language independent. It has been proposed for the Standard, but is not yet part of it. The regular expression pattern for validation is simple.
INSERT INTO Claims -- a mess!
VALUES
('054511', 300.00, '2013-04-00', '2013-04-00', 1)
('054511', 0.00, '2013-05-00', '2013-04-00', 2),
('120301', 250.00, '2015-02-00', '2015-02-00', 1),
('120624', 150.00, '2015-02-00', '2015-02-00', 1),
('120624', 0.00, '2015-03-00', '2015-02-00', 2);
Now, throw this mess out. It looks like your repeat the claim creation date over and over and over. It looks like you crammed a claim creation and a claim history together in one table.
>> I want to isolate rows which appear in the table and do a update using below query (This query is already in a procedure, so I just looking for a suitable way to modify it to support my task).
In the above e.g. ONLY row containing claim_id = '120301' needs to update (amount AS updated_amount)
>> I use following query, but it update other rows as well, I want a suitable query only to capture rows of nature claim_id = '120301' and do this update? <<
No. SQL is set oriented so an update applies to the whole table. You can filter out rows in a WHERE clause.
CREATE TABLE Claims
(claim_id CHAR(5) NOT NULL PRIMARY KEY,
claim_amount DECIMAL (8,2) NOT NULL
CHECK (claim_amount >= 0.00),
claim_creation_month_name CHAR(10) NOT NULL
REFERENCES Month_Period(month_name));
See how this works?
INSERT INTO Claims -- a mess!
VALUES
('054511', 300.00, '2013-04-00'),
('120301', 250.00, '2015-02-00'),
('120624', 150.00, '2015-02-00');
Normalize the table:
CREATE TABLE Claim_Changes
(claim_id CHAR(5) NOT NULL
REFERENCES Claims(claim_id)
ON DELETE CASCADE,
change_month_name CHAR(10) NOT NULL
REFERENCES Month_Period(month_name),
PRIMARY KEY (claim_id, change_month_name),
change_amount DECIMAL (8,2) NOT NULL
CHECK (change_amount >= 0.00)
INSERT INTO Claims_Changes
VALUES
('054511', 0.00, '2013-05-00'),
('120624', 0.00, '2015-03-00');
Now you just add another change row to the history. There is no update. If you want to the delta and so forth, use LAG() and other window functions.
--CELKO-- Books in Celko Series for Morgan-Kaufmann Publishing: Analytics and OLAP in SQL / Data and Databases: Concepts in Practice Data / Measurements and Standards in SQL SQL for Smarties / SQL Programming Style / SQL Puzzles and Answers / Thinking
in Sets / Trees and Hierarchies in SQL

DAQ frequency measurement using anolog input channel

Hello,
I try to develop a DAQ application which run on a real time target.
I want to measure frequency using anolo inpur channel of my DAQ card. I have a problem.
Let me first try to explain what i trying to do. In the first loop i do sampling and show the result as double array.
I need to show samples as double array so i can not read sample as waveform. With a shared variable i sent these samples to second loop.
First loop reriod is msec and second loops period is 20 msec.So when the second loop run, 20 samples were alraady ready, frequency measurement is done.
The problem is that i need to show frequency measurement as far as possible. Say frequency of my signal is about 100 hz, then this
configuration gives correct frequency measurement. But if frequency of the signal is about 10 hz, this configuration fails since period of second loop is 10 msec and it is not enough time to measure a 10 hz signal. But if i adjust period of the second loop as 100msec,
then i can measure 10 hz signal but then i can give measurement of a 100 hz signal +90msec late. What can i do so i can measure frequency af signals ranges 0-100hz and give measurement result as far as possible?
Attachments:
measure_amp_freq.GIF ‏35 KB

eesen,
What you are doing doesn't make any sense to me. First of all, you should take multiple samples with the DAQmx Read and not one sample at time with the timed loop. Your frequency measurement will then actually be more accurate. You also should return a waveform. That includes timing information that the Freq & Amp function needs to determine the frequency. It cannot do it with a dbl array. If you have to display a dbl, then just use the Get Waveform Components to extract the y array. You can get rid of the second timed loop and use a regular loop for the DAQmx Read. If you just set the rate to be twice the highest input frequency and acquire enough samples for a couple of cycles, you should have a pretty accurate reading.

How does select stmt with for all entries uses Indexes

Hello all,
I goes through a number of documents but still confused how does select for all entries uses indexes if fields are not in sequences. i got pretty much the same results if i take like two cases on Hr tables HRP1000 and HRP1001(with for all entries based upon hrp1000). Here is the sequence of index fields on hrp1001 (MANDT, OTYPE, OBJID, PLVAR, RSIGN, RELAT, ISTAT, PRIOX, BEGDA, ENDDA, VARYF, SEQNR). in second case objid field is in sequence as in defined Index but i dont see significant increase in field even though the number of records are around 30000. My question is does it make a differrence to use field sequence (same as in table indexes) in comparison to redundant field sequence (not same as defined in table indexes), secondly how we can ge tto know if table index is used in Select for entries query i tried Explain in ST05 but its not clear if it uses any index at all in hrp1001 read.
here is the sample code i use to get test results.
test case 1
REPORT zdemo_perf_select.
DATA: it_hrp1000 TYPE STANDARD TABLE OF hrp1000 WITH HEADER LINE.
DATA: it_hrp1001 TYPE STANDARD TABLE OF hrp1001 WITH HEADER LINE.
DATA: it_hrp1007 TYPE STANDARD TABLE OF hrp1007 WITH HEADER LINE.
DATA: it_pa0000 TYPE STANDARD TABLE OF pa0000 WITH HEADER LINE.
DATA: it_pa0001 TYPE STANDARD TABLE OF pa0001 WITH HEADER LINE.
DATA: it_pa0002 TYPE STANDARD TABLE OF pa0002 WITH HEADER LINE.
DATA: it_pa0105_10 TYPE STANDARD TABLE OF pa0105 WITH HEADER LINE.
DATA: it_pa0105_20 TYPE STANDARD TABLE OF pa0105 WITH HEADER LINE.
DATA: t1 TYPE timestampl,
      t2 TYPE timestampl,
      t3 TYPE timestampl
SELECT * FROM hrp1000 CLIENT SPECIFIED INTO TABLE it_hrp1000 bypassing buffer
            WHERE mandt EQ sy-mandt AND
                  plvar EQ '01' AND
                  otype EQ 'S'AND
                  istat EQ '1' AND
                  begda <= sy-datum AND
                  endda >= sy-datum AND
                  langu EQ 'EN'.
GET TIME STAMP FIELD t1.
SELECT * FROM hrp1001 CLIENT SPECIFIED INTO TABLE it_hrp1001 bypassing buffer
            FOR ALL ENTRIES IN it_hrp1000
             WHERE mandt EQ sy-mandt AND
                    otype EQ 'S' AND
*                    objid EQ it_hrp1000-objid and
                    plvar EQ '01' AND
                    rsign EQ 'B' AND
                    relat EQ '007' AND
                    istat EQ '1' AND
                    begda LT sy-datum AND
                    endda GT sy-datum and
                    sclas EQ 'C' and
                    objid EQ it_hrp1000-objid.
*                    %_hints mssqlnt 'INDEX(HRP1001~0)'.
*delete it_hrp1001 where sclas ne 'C'.
GET TIME STAMP FIELD t2.
t3 = t1 - t2.
WRITE: 'Time taken - ', t3.
test case 2
REPORT zdemo_perf_select.
DATA: it_hrp1000 TYPE STANDARD TABLE OF hrp1000 WITH HEADER LINE.
DATA: it_hrp1001 TYPE STANDARD TABLE OF hrp1001 WITH HEADER LINE.
DATA: it_hrp1007 TYPE STANDARD TABLE OF hrp1007 WITH HEADER LINE.
DATA: it_pa0000 TYPE STANDARD TABLE OF pa0000 WITH HEADER LINE.
DATA: it_pa0001 TYPE STANDARD TABLE OF pa0001 WITH HEADER LINE.
DATA: it_pa0002 TYPE STANDARD TABLE OF pa0002 WITH HEADER LINE.
DATA: it_pa0105_10 TYPE STANDARD TABLE OF pa0105 WITH HEADER LINE.
DATA: it_pa0105_20 TYPE STANDARD TABLE OF pa0105 WITH HEADER LINE.
DATA: t1 TYPE timestampl,
      t2 TYPE timestampl,
      t3 TYPE timestampl
SELECT * FROM hrp1000 CLIENT SPECIFIED INTO TABLE it_hrp1000 bypassing buffer
            WHERE mandt EQ sy-mandt AND
                  plvar EQ '01' AND
                  otype EQ 'S'AND
                  istat EQ '1' AND
                  begda <= sy-datum AND
                  endda >= sy-datum AND
                  langu EQ 'EN'.
GET TIME STAMP FIELD t1.
SELECT * FROM hrp1001 CLIENT SPECIFIED INTO TABLE it_hrp1001 bypassing buffer
            FOR ALL ENTRIES IN it_hrp1000
             WHERE mandt EQ sy-mandt AND
                    otype EQ 'S' AND
                    objid EQ it_hrp1000-objid and
                    plvar EQ '01' AND
                    rsign EQ 'B' AND
                    relat EQ '007' AND
                    istat EQ '1' AND
                    begda LT sy-datum AND
                    endda GT sy-datum and
                    sclas EQ 'C'." and
*                    objid EQ it_hrp1000-objid.
*                    %_hints mssqlnt 'INDEX(HRP1001~0)'.
*delete it_hrp1001 where sclas ne 'C'.
GET TIME STAMP FIELD t2.
t3 = t1 - t2.
WRITE: 'Time taken - ', t3.

Mani wrote:
Thank you for your answer, its very helpful but i am still nor sure how does parameter rsdb/max_blocking_factor affect records size.
Hi,
The blocking affects the size of the statement and the memory structures for returning the result.
So if your itab has 500 rows and your blocking is 5, the very same statement will be executed 100 times.
Nothing good or bad about this so far.
Assume, your average result for an inlist 5 statement is 25 records with an average size of 109 bytes.
You average result size will be 2725 byte plus overhead which will nearly perfectly fit into two 1500 byte ethernet frames.
Nothing to do in this case.
Assume your average result for an inlist 5 statement is 7 records with an average size of 67 bytes.
You average result size will be ~ 470 byte plus overhead which will only fill 1/3 of a 1500 byte ethernet frame.
In this case, setting the blocking to 12 ... 15 will give you 66% network transfer performance gain,
and reduces the number of calls to the DB by 50%, giving additional benefit.
Now this is an extreme example. The longer the average row length is, the lower will be the average loss in the network.
You have the same effects in memory structures, but on that layer you are fighting single micro seconds instead of
hundreds of these, so in real life it is rarely measurable.
Depending on table-statistics, oracle might decide for short inlists to use a concatanation instead of an inlist.
This is supposed to be more costy, but I never had a case where I could proove a big difference.
Values from 5 to 15 for blocking seem to be ok for me. If you have special statements in customer coding,
it #might# be benefitial to do the mentioned calculations and do some network tracing to see if you can squeeze your
network efficiency by tuning the blocking.
If you have jumbo frames enabled, it might be worth to be analyzed as well.
If you are only on a DB-CI system that is loopback connected to the DB, I doubt there might be a big outcome.
Hope this helps
Volker

How to use a photogate for frequency measurement using a NI USB-6211

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