The dataTaker 50 data logger has 5 digital input channels, and the dataTaker 500/600 series loggers have 4 digital input channels, which can be used as counters.

The Channel Expansion Module (CEM-AD) have 20 digital input channels which however cannot be used as counters.

The digital input channels of the dataTaker can be used to count digital pulses in any of four modes

accumulating counters, which totalise digital pulses forever. When accumulating counters are read, the current contents of the counter registers are returned

resetting counters, which totalise digital pulses during the interval between readings. When resetting counters are read, the current contents of the counter registers are returned, and the register is reset to zero

accumulating Phase Encoder counter, which increments or decrements counts depending on the phase relationship between pulses input on two digital channels. When the Phase Encoder counter is read as an accumulating counter, the contents of the counter register is returned.

resetting Phase Encoder counter, which increments or decrements counts depending on the phase relationship between pulses input on two digital channels. When the Phase Encoder counter is read as a resetting counter, the contents of the counter registers are returned and the register is reset to zero

Individual counters cannot be simultaneously used as accumulating and resetting countersñ if you need total and interval counts, then input the same pulse train into two channels, and run one as an accumulating counter and the other as a resetting counter.

The counters associated with the digital channels of the dataTaker are all software counters.

The low speed counters are 16 bit up counters, and have a count range of 0 to 65535. The counters begin at zero counts, count up to 65535, 'roll over' to 0 on the next count, and then continue to count upwards.

The Phase Encoder counter is a 16 bit up down counter, and has a count range of
–32768 to 0 to 32767. The counter begins at zero counts, and counts upwards or downwards depending on the phasic relationship of the two input pulse trains.

The low speed counters increment when the state of the digital input switches from high (logic 1) to low (logic 0).

Maximum Counting Rate

All digital counters have 10 Hz count rate capability by default. The maximum count rate is determined by the digital input channel sample period Parameter13, and the number of counters in use.

By default, Parameter13 is set to a sample period of 50 mSec. This means that the digital inputs are sampled every 50 mSec, and so the maximum discernable count rate is 1000/(50 x 2) = 10Hz. If a pulse rise and fall occurs in less than 50 mSec (ie. in the same sample period), then the pulse will not be registered or counted.

Higher count rates of up to 500 Hz can be achieved if the digital input sample period reduced (digital sampling rate is increased) and other time consuming tasks such as communications, analog to digital conversion, etc. are kept to a minimum.

Using DeTransfer, the digital sampling period is set by the command for example

sets the period to 10 mSec, and translates to a maximum count rate of 1000/(10 x 2) = 50Hz.

Using DeLogger, the digital sampling period is set in the Program Builder under the Settings tab,. Right click the Special Commands button to open the dialog, and enter the Parameter13 command in the Optional Initialization Commands window.

 

 

Low Power Mode

The digital input channels of the dataTaker are powered down whenever the logger is operating in the low power mode. The digital channels will not register or count any changes of state on the inputs while powered down.

Therefore the low speed counters cannot be used if the logger is to be operated in the low power mode. However, the high speed counters can still be used.

Counts received by the low speed counters while the logger is awake are registered, counted and saved. Although counts are not registered while the logger is asleep, new counts will continue to be counted from the current value of the counters when the logger next wakes.

Connecting Low Speed Counter Inputs

The low speed count inputs are connected to the digital input channels between the selected digital input channel terminal, and any GND or unused Analog Return terminal as follows

 

 

Figure 115 ñ Connecting a Low Speed Count Signal

Caution : If the Analog Return terminal is used, this is 100 Ω above the dataTaker ground.

Reading as Accumulating Counters

The low speed counters of the digital input channels are operated as accumulating counters, and the count data is returned to the host, when a Schedule containing the channel is executed.

Using DeTransfer, the command for example

instructs the dataTaker to read the current value for the low speed counters for digital channels 1 and 3.

The C specifies an accumulating low speed counter.

Using DeLogger, the low speed counters can be read as accumulating counters by the following Program Builder program. The accumulating counter mode is selected directly from the channel selection walking menu.

 

 

The data is returned in units of Counts. Each successive reading is the accumulation of counts since the command/program was entered into the dataTaker.

The dataTaker will read the counter every 5 minutes, and readings are stopped by the H (Halt) command.

Reading as Resetting Counters

The low speed counters of the digital input channels are operated as resetting counters, and the count data is returned to the host, when a Schedule containing the channel is executed. The counter is reset each time that it is read.

Using DeTransfer, the command for example

instructs the dataTaker to read the current value for the low speed counter channels 1 and 2.

The C specifies a low speed counter. The R channel option indicates the counter is to be reset to zero when read.

Using DeLogger, the low speed counters can be read as resetting counters by the following Program Builder program. The resetting counter mode is selected directly from the channel selection walking menu.

 

 

The data is returned in units of Counts. Each successive reading is the accumulation of counts since the command/program was entered into the dataTaker.

The dataTaker will read the counters every 5 minutes, and readings are stopped by the H (Halt) command.

Programming and operation of the low speed counters is described in detail in Section III ñ The Counter Channels.