Data Interval/Change Trigger - Revision history

Mparadis: /* Data Rate */

2023-07-27T14:34:34Z

Data Rate

← Older revision		Revision as of 14:34, 27 July 2023
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	=== Data Rate===		=== Data Rate===
	DataRate is the reciprocal of DataInterval: instead of being measured in milliseconds between data samples, it is measured in hertz (the number of samples provided within one second). When you set the DataInterval for your device, the DataRate will also be set to the corresponding value and vice-versa. In the Phidget Control Panel, you can click on the DataInterval in order to switch between the two. In most cases, whether you use one or the other is a matter of personal preference. However, for devices that can provide data in faster than 1ms intervals, you must use Data Rate to get the most data because DataInterval is an integer and can't go below 1 millisecond.		DataRate is the reciprocal of DataInterval: instead of being measured in milliseconds between data samples, it is measured in hertz (the number of samples provided within one second). When you set the DataInterval for your device, the DataRate will also be set to the corresponding value and vice-versa. In the Phidget Control Panel, you can click on the DataInterval in order to switch between the two. In most cases, whether you use one or the other is a matter of personal preference. However, for devices that can provide data in faster than 1ms intervals, you must use Data Rate to get the most data because DataInterval is an integer and can't go below 1 millisecond.

			While the Phidgets libraries will allow you to set any value within the specified minimum and maximum for your device, sometimes hardware limitations cause certain data rates to be unavailable. In this case, the nearest possible data rate will be selected instead. For more details on this behaviour, see the Advanced Topics section below.

	== Change Trigger ==		== Change Trigger ==

Mparadis at 17:21, 26 July 2023

2023-07-26T17:21:54Z

← Older revision		Revision as of 17:21, 26 July 2023
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	The change is possible because a <code>PropertyChanged</code> event is thrown in both of these cases. If you want to use this event in your program, you can read more about it by going to the {{Phidget22API}} and selecting the "PhidgetAPI" section for your device.		The change is possible because a <code>PropertyChanged</code> event is thrown in both of these cases. If you want to use this event in your program, you can read more about it by going to the {{Phidget22API}} and selecting the "PhidgetAPI" section for your device.
			}}
			{{UGC-Entry\|Why am I getting data at a different DataInterval or DataRate than what was set?\|\|
			There are a couple of factors that affect the rate at which data can be sent, such as ADC limitations and communication speed limits. Because of this, you may try to set the DataRate to 300Hz, but only get data at 250Hz. Usually the device will set the next-slowest possible rate than what was requested. If you want to know for certain what rate is actually being used, you can check the <code>DataRate</code> property after setting it.

			You can also use the Phidget Control Panel to test this behaviour on your devices. When you click on the graph button beside your data readout, you can see the real data rate on the bottom of the graph:

			[[File:realDataRate.jpg\|link=]]

			The first number is the result of getting the <code>DataRate</code> value from the API, and the second number is the result of a manual time calculation of the data coming in (if the numbers don't match, it could indicate latency issues or a bug in the device firmware).
	}}		}}
	{{UGC-Entry\|What happens when both Data Interval and Change Trigger are set?\|\|		{{UGC-Entry\|What happens when both Data Interval and Change Trigger are set?\|\|

Mparadis: /* Data Interval and Data Rate */

2023-07-25T22:13:07Z

Data Interval and Data Rate

← Older revision		Revision as of 22:13, 25 July 2023
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	==Data Interval and Data Rate==		==Data Interval and Data Rate==

			=== Data Interval ===
	The <code>DataInterval</code> property, measured in milliseconds, determines the rate at which the device channel will report data back to your program. If a channel is open in more than one program (i.e. with remote connections over the [[Phidget Network Server]]), all instances of that channel will share one data interval, and changing it in one program will change it in all others. When this change occurs, a <code>PropertyChange</code> event will be triggered in each of the other programs so they can adjust accordingly if needed.		The <code>DataInterval</code> property, measured in milliseconds, determines the rate at which the device channel will report data back to your program. If a channel is open in more than one program (i.e. with remote connections over the [[Phidget Network Server]]), all instances of that channel will share one data interval, and changing it in one program will change it in all others. When this change occurs, a <code>PropertyChange</code> event will be triggered in each of the other programs so they can adjust accordingly if needed.

Mparadis: /* Advanced Topics */

2023-07-25T22:12:11Z

Advanced Topics

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 == Advanced Topics ==
 {{UGC-Entry|What happens when both Data Interval and Change Trigger are set?||
 In some complex situations, you may want to set both the <code>ChangeTrigger</code> and the <code>DataInterval</code> to non-trivial values. This will result in expected behavior: The channel will check at the <code>DataInterval</code> whether or not the new data differs from the last delivered data by an amount greater than or equal to the <code>ChangeTrigger</code>. If the data passes the ''change trigger'' filter, that data will be delivered, if the data does not,  the channel will wait until the next ''data interval'' and check again.

Mparadis at 22:03, 21 July 2023

2023-07-21T22:03:10Z

← Older revision		Revision as of 22:03, 21 July 2023
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	[[Category:Programming]]		[[Category:Programming]] __NOTOC__
	__NOTOC__
	[[Image:DataIntervalRate.jpg\|link=\|right]]		[[Image:DataIntervalRate.jpg\|link=\|right]]
	Phidget devices often send streams of sensor and state data to attached channels. The rate at which that data is delivered can be controlled by setting the <code>DataInterval</code> property of a channel. A threshold can be set to filter data that does not vary by more than a defined amount by setting the <code>ChangeTrigger</code> property of a channel.		Phidget devices often send streams of sensor and state data to attached channels. The rate at which that data is delivered can be controlled by setting the <code>DataInterval</code> property of a channel. A threshold can be set to filter data that does not vary by more than a defined amount by setting the <code>ChangeTrigger</code> property of a channel.

Mparadis at 22:02, 21 July 2023

2023-07-21T22:02:30Z

← Older revision		Revision as of 22:02, 21 July 2023
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	==Data Interval and Data Rate==		==Data Interval and Data Rate==

	The <code>DataInterval</code> property, measured in milliseconds, determines the rate at which the device channel will report data back to your program. If a channel is open in more than one program (i.e. with remote connections over the [[Phidget Network Server]]), all instances of that channel will share one data interval, and changing it in one program will change it in all others. When this change occurs, a <code>PropertyChange</code> event will be triggered in each of the other programs so they can adjust accordingly if needed.		The <code>DataInterval</code> property, measured in milliseconds, determines the rate at which the device channel will report data back to your program. If a channel is open in more than one program (i.e. with remote connections over the [[Phidget Network Server]]), all instances of that channel will share one data interval, and changing it in one program will change it in all others. When this change occurs, a <code>PropertyChange</code> event will be triggered in each of the other programs so they can adjust accordingly if needed.

Mparadis at 22:02, 21 July 2023

2023-07-21T22:02:21Z

← Older revision		Revision as of 22:02, 21 July 2023
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	=== Data Rate===		=== Data Rate===
	DataRate is the reciprocal of DataInterval: instead of being measured in milliseconds between data samples, it is measured in hertz (the number of samples provided within one second). When you set the DataInterval for your device, the DataRate will also be set to the corresponding value and vice-versa. In the Phidget Control Panel, you can click on the DataInterval in order to switch between the two. In most cases, whether you use one or the other is a matter of personal preference. However, for devices that can provide data in faster than 1ms intervals, you must use Data Rate to get the most data because DataInterval is an integer and can't go below 1 millisecond.		DataRate is the reciprocal of DataInterval: instead of being measured in milliseconds between data samples, it is measured in hertz (the number of samples provided within one second). When you set the DataInterval for your device, the DataRate will also be set to the corresponding value and vice-versa. In the Phidget Control Panel, you can click on the DataInterval in order to switch between the two. In most cases, whether you use one or the other is a matter of personal preference. However, for devices that can provide data in faster than 1ms intervals, you must use Data Rate to get the most data because DataInterval is an integer and can't go below 1 millisecond.


	== Change Trigger ==		== Change Trigger ==

Mparadis at 22:02, 21 July 2023

2023-07-21T22:02:00Z

← Older revision		Revision as of 22:02, 21 July 2023
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	Phidget devices often send streams of sensor and state data to attached channels. The rate at which that data is delivered can be controlled by setting the <code>DataInterval</code> property of a channel. A threshold can be set to filter data that does not vary by more than a defined amount by setting the <code>ChangeTrigger</code> property of a channel.		Phidget devices often send streams of sensor and state data to attached channels. The rate at which that data is delivered can be controlled by setting the <code>DataInterval</code> property of a channel. A threshold can be set to filter data that does not vary by more than a defined amount by setting the <code>ChangeTrigger</code> property of a channel.

	Phidget device channels are initialized with a <code>DataInterval</code> specific to the device ~~channel,~~ and a <code>ChangeTrigger</code> of zero when they are attached. See the {{Phidget22API}} for more information.		Phidget device channels are initialized with a default <code>DataInterval</code> specific to the device and a <code>ChangeTrigger</code> of zero when they are attached. See the {{Phidget22API}} for more information.

			In most cases, it is likely that you'll simply use these properties as follows:

			* Keep the <code>ChangeTrigger</code> at zero and select the <code>DataInterval</code> based on how often you want your program to receive data. This configuration is useful in data logging applications and when data will be represented in a graph.
			* Or, keep the <code>DataInterval</code> at a minimal interval, and set the <code>ChangeTrigger</code> to the lowest relevant value for the quality you are measuring. This is useful for applications were you want to ignore values below a certain threshold or are displaying sensor values to be read in real-time.

			Keep reading below for more details on these properties.

	==Data Interval and Data Rate==		==Data Interval and Data Rate==
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	It can be useful to set a ''change trigger'' to reduce amount of data, only receiving data change events when meaningful thresholds are reached. For example, an application that displayed temperature on an LCD may only be interested on 0.5°C changes. By setting the <code>ChangeTrigger</code> to 0.5, you could avoid having a fast-changing number that is difficult to read, without sacrificing response time.		It can be useful to set a ''change trigger'' to reduce amount of data, only receiving data change events when meaningful thresholds are reached. For example, an application that displayed temperature on an LCD may only be interested on 0.5°C changes. By setting the <code>ChangeTrigger</code> to 0.5, you could avoid having a fast-changing number that is difficult to read, without sacrificing response time.

	~~In most cases, it is likely that you'll simply use these properties as follows:~~

	* Keep the <code>ChangeTrigger</code> at zero and select the <code>DataInterval</code> based on how often you want your program to receive data. This configuration is useful in data logging applications and when data will be represented in a graph.
	* Keep the <code>DataInterval</code> at a minimal interval, and set the <code>ChangeTrigger</code> to the lowest relevant value for the quality you are measuring. This is useful for applications were you want to ignore values below a certain threshold or are displaying sensor values to be read in real-time.


	== Advanced Topics ==		== Advanced Topics ==

Mparadis at 21:59, 21 July 2023

2023-07-21T21:59:39Z

← Older revision		Revision as of 21:59, 21 July 2023
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	=== Data Rate===		=== Data Rate===
	DataRate is the reciprocal of DataInterval: instead of being measured in milliseconds between data samples, it is measured in hertz (~~how many~~ samples provided within one second).		DataRate is the reciprocal of DataInterval: instead of being measured in milliseconds between data samples, it is measured in hertz (the number of samples provided within one second). When you set the DataInterval for your device, the DataRate will also be set to the corresponding value and vice-versa. In the Phidget Control Panel, you can click on the DataInterval in order to switch between the two. In most cases, whether you use one or the other is a matter of personal preference. However, for devices that can provide data in faster than 1ms intervals, you must use Data Rate to get the most data because DataInterval is an integer and can't go below 1 millisecond.

Mparadis at 21:55, 21 July 2023

2023-07-21T21:55:42Z

← Older revision		Revision as of 21:55, 21 July 2023
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	[[Category:Programming]]		[[Category:Programming]]
			__NOTOC__
	[[Image:DataIntervalRate.jpg\|link=\|right]]		[[Image:DataIntervalRate.jpg\|link=\|right]]
	Phidget devices often send streams of sensor and state data to attached channels. The rate at which that data is delivered can be controlled by setting the <code>DataInterval</code> property of a channel. A threshold can be set to filter data that does not vary by more than a defined amount by setting the <code>ChangeTrigger</code> property of a channel.		Phidget devices often send streams of sensor and state data to attached channels. The rate at which that data is delivered can be controlled by setting the <code>DataInterval</code> property of a channel. A threshold can be set to filter data that does not vary by more than a defined amount by setting the <code>ChangeTrigger</code> property of a channel.
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	==Data Interval and Data Rate==		==Data Interval and Data Rate==

	The <code>DataInterval</code> property ~~of a channel~~ determines the rate at which the device channel will report data back to your program. If a channel is open in more than one program (i.e. with remote connections over the [[Phidget Network Server]]), all instances of that channel will share one data interval, and changing it in one program will change it in all others. When this change occurs, a <code>PropertyChange</code> event will be triggered in each of the other programs so they can adjust accordingly if needed.		The <code>DataInterval</code> property, measured in milliseconds, determines the rate at which the device channel will report data back to your program. If a channel is open in more than one program (i.e. with remote connections over the [[Phidget Network Server]]), all instances of that channel will share one data interval, and changing it in one program will change it in all others. When this change occurs, a <code>PropertyChange</code> event will be triggered in each of the other programs so they can adjust accordingly if needed.

	The minimum, maximum and default DataInterval varies for each device. Refer to the {{Phidget22API}} and check the <code>MinDataInterval</code> and <code>MaxDataInterval</code> properties for your device to see the limits. In most cases, you will probably want to set the DataInterval to the minimum value to get as much data as possible. However, in some applications such as long-run data logging, you may want to increase DataInterval to make the resulting data set more manageable. You may also want to increase the DataInterval if you're using a PhidgetSBC or HUB5000, since they can be overwhelmed if too many channels are running at the minimum DataInterval.		The minimum, maximum and default DataInterval varies for each device. Refer to the {{Phidget22API}} and check the <code>MinDataInterval</code> and <code>MaxDataInterval</code> properties for your device to see the limits. In most cases, you will probably want to set the DataInterval to the minimum value to get as much data as possible. However, in some applications such as long-run data logging, you may want to increase DataInterval to make the resulting data set more manageable. You may also want to increase the DataInterval if you're using a PhidgetSBC or HUB5000, since they can be overwhelmed if too many channels are running at the minimum DataInterval.

			=== Data Rate===
			DataRate is the reciprocal of DataInterval: instead of being measured in milliseconds between data samples, it is measured in hertz (how many samples provided within one second).


	== Change Trigger ==		== Change Trigger ==
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	The <code>ChangeTrigger</code> property of a channel enables a filter that only passes data when that data has changed by an amount greater than or equal to the <code>ChangeTrigger</code>. For example, if the <code>DataInterval</code> was set to 0.7, new data would only be delivered to the channel when that new data differed from the previously delivered data by at least 0.7.		The <code>ChangeTrigger</code> property of a channel enables a filter that only passes data when that data has changed by an amount greater than or equal to the <code>ChangeTrigger</code>. For example, if the <code>DataInterval</code> was set to 0.7, new data would only be delivered to the channel when that new data differed from the previously delivered data by at least 0.7.

	It ~~is often~~ useful to set a ''change trigger'' to reduce ~~the apparent noise on a channel~~, ~~or to~~ only ~~receive~~ data change events when meaningful thresholds are reached. For example, an application that displayed temperature on an LCD may only be interested on 0.5°C changes. By setting the <code>ChangeTrigger</code> to 0.5, ~~the only data~~ that ~~would be receive would be data of interest~~.		It can be useful to set a ''change trigger'' to reduce amount of data, only receiving data change events when meaningful thresholds are reached. For example, an application that displayed temperature on an LCD may only be interested on 0.5°C changes. By setting the <code>ChangeTrigger</code> to 0.5, you could avoid having a fast-changing number that is difficult to read, without sacrificing response time.

	In most cases, it is likely that you'll simply use these properties as follows:		In most cases, it is likely that you'll simply use these properties as follows:

	* Keep the <code>ChangeTrigger</code> at zero and select the <code>DataInterval</code> based on how often you want your program to receive data. This configuration is useful in data logging applications and when data will be represented in a graph.		* Keep the <code>ChangeTrigger</code> at zero and select the <code>DataInterval</code> based on how often you want your program to receive data. This configuration is useful in data logging applications and when data will be represented in a graph.
	* Keep the <code>DataInterval</code> at a minimal interval, and set the <code>ChangeTrigger</code> to the lowest relevant value for the quality you are measuring. This is useful for applications were you want to ignore values below a certain threshold or are displaying sensor values.		* Keep the <code>DataInterval</code> at a minimal interval, and set the <code>ChangeTrigger</code> to the lowest relevant value for the quality you are measuring. This is useful for applications were you want to ignore values below a certain threshold or are displaying sensor values to be read in real-time.