Agilent Technologies DP111 - Manual (Page 23)

User Manual: Agilent Acqiris 8-bit Digitizers Page 23 of 59
For 1 M Ω coupling in the DC2x1A/AR, DC140HZ, and U1071AHZ1 the 700 MHz Bandwidth Limiter cannot be
used. Furthermore, in the DC2x1A/AR, DC1xxHZ, and U1071AHZn with FS gain > 5V the 200 MHz Bandwidth
Limiter is always active.
3.2.6. Input Voltage and Offset
The input channel provides a fully programmable amplifier with variable input voltage and offset. Full Scale (FS)
input voltages are selectable from 50 mV to 5 V (except as shown above) in a 1, 2, 5 sequence. Care should be taken
to select an input voltage range that will allow the signal to be recorded using as much dynamic range of the digitizer
as possible. The Variable Offset is programmable in the range of ±2 V when using an FS Input Voltage setting of
500 mV or below, increasing to ± Maximum Offset for FS settings above 500 mV. The raw 8-bit ADC data values
are in the range [-128,+127] with the first and last values reserved for underflow and overflow respectively. The
midpoint value, 0, of the range corresponds to the negative of the offset voltage. Thus the Full Scale Range (FSR)
goes from
–Offset Voltage – (FS/2) to –Offset Voltage + (FS/2)
Signals going outside of the FSR will be clipped and data values for the clipped portion of a signal should be
regarded as erroneous.
The maximum input voltage for 50 Ω input impedance is ±5 V. The maximum input for 1 MΩ input impedance is
±100 V (dc + ac) except for the DC2x1A/AR models where it is ±300 V (dc + ac).
3.2.7. Vertical Resolution
The digitizers described in this manual use an ADC system with 8 bits of vertical resolution (256 levels). The
dynamic range of the ADC covers the Full Scale Range (FSR) of the Input Voltage setting. For example, if the Input
Voltage is set to 1 V then the ADC resolution is equivalent to 3.91 mV. To obtain the best dynamic range from the
ADC care should be taken to ensure that the input signal varies over more than 50% of the Input Voltage FSR
setting.
3.2.8. DC Accuracy and Linearity
The DP and DC Series digitizers use low noise front-end electronics in order to ensure voltage measurement is made
with accuracy and precision. DC voltage accuracy, at 0 V offset, is better than ±2% (±1% typical) of the input
voltage full scale. The differential linearity is better than ±0.7 LSB ( ±0.8 LSB for DC135/DC140 digitizers and
±0.9 LSB for other DC271-FAMILY digitizers).
3.2.9. Using Probes
The 50 Ω and 1 MΩ input impedance settings make it possible to use Acqiris digitizers with a wide variety of
probes. The 50 Ω setting is most commonly used for active probes and low impedance (500 Ω) passive probes. The
1 M Ω setting is normally used for high impedance probes. Before using any passive probe with a digitizer care
should be taken to check that the probe has been correctly adjusted (refer to the Probe’s Calibration procedure).
NOTE: Passive high impedance probes are not suitable for high fidelity measurements above 100 MHz. The non-
negligible (5-10 pF) tip capacitance loads the signal causing distortion and/or ringing when combined with the
ground lead inductance.
3.3. Data Acquisition
The table below summarizes the characteristics discussed in the sections that follow:
Model Max.
Sampling
Rate
Max.
CONVER
TERS PER
CHANNEL/
CHANNELS Default
Memory
samples/
channel
Maximum
Optional
Memory
samples/
channel
Maximum
Segments
TTI
Reso-
lution
Timebase
Accuracy
External
Clock
Max./
Min.
Thresh.
DP105
500 MS/s 1 / 1 128K 8M 8000 80 ps 50 ppm ± 2 V
DP106 500 MS/s 1 / 1 128K 2M 4000 80 ps 50 ppm ± 2 V
DP110 1 GS/s 1 / 1 128K 8M 8000 80 ps 50 ppm ± 2 V
DP111 1 GS/s 1 / 1 128K 2M 4000 5 ps 2 ppm ± 3 V