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QL Series II Technical Specifications

QL Series II Single output power supply

QL Series II DC Supplies

  • Advanced dc power supplies, single or triple output
  • Very high precision, very low noise, excellent dynamics
  • Advanced user interface with numeric and rotary control
  • Multiple voltage/current ranges for increased flexibility
  • Multiple non-volatile memories for power supply set-ups
  • Switchable remote sense provides perfect load regulation
  • Comprehensive protection including OVP and OCP trips
  • Compact bench footprint; modular width for rack mounting
  • Auxiliary output fully variable 1.00V to 6.00V at 3A with selectable voltage and current metering (T models)
  • Bus programmable via USB, RS232, GPIB or LAN (P models) LAN interface is LXI class C compliant
  • Duplicate power and sense terminals at rear (P models)


QL355, QL355P, QL355T, QL355TP
Max. Output Power105 watts
Output Ranges Range 1 - 0 to 35V, 0 to 3A
Range 2 - 0 to 15V, 0 to 5A
Range 3 - 0 to 35V, 0 to 500.0mA
QL564, QL564P, QL564T, QL564TP
Max. Output Power112 watts
Output Ranges Range 1 - 0 to 56V, 0 to 2A
Range 2 - 0 to 25V, 0 to 4A
Range 3 - 0 to 56V, 0 to 500.0mA
All Models
Voltage SettingBy floating point numeric entry or rotary jog wheel; resolution 1mV
Current SettingBy floating point numeric entry or rotary jog wheel; resolution 1mA or 0.1mA depending on range
Setting AccuracyVoltage - 0.03% ±5mV
Current 0.2% ±5mA/0.5mA
Output ModeOperation in constant voltage or constant current modes with automatic cross-over and mode indication
DC Output SwitchSets output voltage and current levels to zero when Off
Output Terminals4mm safety binding post terminals on 19mm (0.75") spacing. Duplicated on rear terminal block (P versions only)
Load RegulationFor any load change, at the output terminals, using remote sense, Voltage <0.01% + 2mV. Current <0.01% + 250µA; <0.01% +50µA on 500mA range.
(Add typically 2.5mV for a 0.5V drop in the positive output lead.)
Line RegulationVoltage <0.01% + 2mV for 10% change.Current <0.01% +250µA; <0.01%+ 50µA on 500mA range
Ripple and NoiseTypically <0.35mV rms CV mode, and <0.2mA rms CI mode (<20µA rms on 500mA range)
Common Mode Noise Current<4µA rms at 20MHz bandwidth
Transient Response<20usec to within 15mV of setting for 90% load change
Temperature Coefficient<(50ppm+0.5mV)/ °C (voltage), <(100ppm+1mA/0.1mA)/°C (current)
Remote SenseEliminates up to 0.5V drop per lead. Remote sense operation selected from front panel and indicated by LED
Sense TerminalsRecessed sprung sockets for direct insertion of wires. Duplicated on rear terminal block (P versions only)

Output ProtectionOutput will withstand forward voltages of up to 20V above rated output voltage. Reverse protection by diode clamp for currents up to 3A
Fault Condition TripThe output will be shut down if any of the four trip conditions listed below occur. (In addition to the output being set to Off, an isolated rear panel signal is also activated.)
Over Voltage (OVP)Settable 1V to 40V (QL355) or 60V (QL564) in 0.1V steps
Over Current (OCP)Settable 0.1A to 5.5A (QL355) or 4.5A (QL564) in 0.01A steps
Over TemperatureMonitors internal temperature rise to protect against excess ambient temperature or blocked ventilation slots
Sense ErrorMonitors the voltage between the remote sense terminals and output terminals to protect against mis-wiring
Trip Output SignalIsolated open-collector output signal on rear panel

Display TypeDual digital displays per output using 14mm (0.56") high brightness LEDs. 5 digits for voltage, 4 digits for current. Update rate 4 per second.
Meter FunctionVoltage meter shows set voltage when in CV mode and measured voltage when in CI mode.
Current meter shows measured current when in CV mode and set current when in CI mode.
Limits DisplayWith the dc output switch set to Off, both meters show the set values (i.e. the limits).
With the output On, either the voltage meter or current meter will show a measured value (depending on the CV/CI mode). Pressing the Limits button will provide a temporary display of the set values.
Watts (VxA) DisplayThe voltage meter can be made to show the calculated product of voltage and current
Meter Resolution
Voltage1mV (CV mode) or 10mV (CI mode)
Current1mA or 0.1mA depending on range
Power0.01W or 0.001W depending on range
Meter Accuracy
Voltage0.1% of reading ±10 mV (CI mode)
Current0.2% of reading ± 0.005A or 0.5mA (CV mode)
Power0.3% of reading ± 0.05W or 0.005W

Main Output(s)Up to 50 set-ups per output can be saved and recalled via the keyboard or remote interfaces.
Parameters StoredRange, Set volts, Set current, OVP, OCP
Recall systemSettings are previewed onto the displays before being actioned
Linked ModeOn triple output models when in Linked mode, a further set of 50 memories stores and recalls values for both outputs simultaneously
Auxiliary OutputUp to 10 voltage settings can be saved and recalled via the keyboard or remote interfaces

Isolated rear-panel open-collector output signal. User can select output to be activated for either OVP, OCP, Overtemperature or Sense miswiring, or for any of those four faults.

(Triple Output Models) Each output can be controlled independently or can be linked. When linked, keyboard and jog wheel control operates on both outputs simultaneously.

Linked mode can be used to create tracking outputs, or for convenient series or parallel operation of the two outputs.

A Copy function is available which copies all of the settings for output 1 to output 2 (Range, Set volts, Set current, OVP, OCP).

Linked mode can also be used to store the settings for both outputs to a group of common memory stores when simultaneous recall is required.

(Note: Linked mode can be selected with differing voltage and current settings on the two outputs. However both outputs must be set to the same range.)

(Triple Output Models)
Output Voltage 1.00 to 6.00V
Output Current>3.0 A maximum. LED indication of over-current
DC Output SwitchSets output voltage level to zero when Off
Setting Accuracy0.5% ±10mV
Ripple and Noise<2mV rms, 10mVp-p
Load Regulation< 1% for 90% load change
Line Regulation< 0.1% for 10% line change
Meter AccuracyVoltage 0.5% ±10mV, Resolution 10mV
Current 0.5% ±10mA, Resolution 10mA
Output RegulationSwitch-mode down converter
Output ProtectionOutput will withstand up to 16 V forward voltage. Diode clamped for reverse voltages and 1 Amps reverse current
Output Terminals4mm safety binding post terminals on 19mm (0.75") spacing. Duplicate screwless terminals at rear (P versions only)

(P suffix versions only) Full remote control and read-back using RS-232, USB, GPIB or LAN (compliant with LXI class C). All interfaces are at ground potential and opto-isolated from the output terminals
RS-232Standard 9-pin D connector. Baud rate variable 600 to 19,200
USBUSB 2.0 connection (backwards compatible with USB 1.x). Operates as a virtual COM port
GPIB (IEEE-488)The interface conforms with IEEE-488.1 and IEEE-488.2
Ethernet (LAN)Standard 10/100 base-T hardware connection. ICMP and TCP/IP Protocol for connection to Local Area Network or direct connection to a single PC
LXI ComplianceLAN interface is compliant with LXI class C. (LXI is the abbreviation for LAN eXtensions for Instrumentation). For more information please see our LXI page

(P versions only)
Voltage Setting - Main Output(s)
Resolution/Accuracy1mV / ± (0.03% +5mV)
Current Setting - Main Output(s)
Resolution/Accuracy0.1mA / ± (0.2% +5mA) or 0.01mA / ± (0.2% +0.5mA) on 500mA range
Voltage Setting - Auxiliary Output (Triple Output Models)
Resolution/Accuracy10mV / ± (0.5% +10mV)
Programming Speed
Command DelayTypically <25ms (this must be added to any of the figures below)
Voltage Up Time<10ms* to 1%
Voltage Down Time<40ms* to 1% (full load); <0.6s* to 1% (no load)
* The up and down times vary with range and voltage step size. More information is contained in the operating manual

IVI DriverAn IVI driver for Windows is supplied. This provides support for common applications such as LabView*,
LabWindows*, HPVEE* etc.
USB DriverAn installation file is supplied which calls a standard Windows* USB driver.
* LabView and LabWindows are trademarks of National Instruments.
HPVEE (now Agilent VEE) is a trademark of Agilent Technologies.
* USB interface is supported for Windows 2000, XP, Vista and Windows 7. Further versions will be
supported as they are released. Windows is a trademark of Microsoft.

All functions, including the selection and set-up of the remote control interfaces, can be set from the keyboard. The rotary jog control can be used to adjust output voltage and current settings in a quasi-analogue mode.

AC Input 230V AC or 115V AC ± 10%, 50/60HzInstallation Category II
Input PowerSingle - 250VA max.
Triple - 500VA max
Temperature & Environmental
Operating Range+5°C to +40°C, 20% to 80% RH
Storage Range-40°C to + 70°C
EnvironmentalIndoor use at altitudes up to 2000m, Pollution Degree 2
CoolingIntelligent variable-speed fan. Over-temperature trip shuts down output if internal temperatures exceed predetermined thresholds.
Safety & EMC
SafetyComplies with EN61010-1
EMCComplies with EN61326

(size excludes feet, knobs and terminals)
Single140 x 160 (1/3 rack, 4U) x 290mm
Triple280 x 160 (2/3 rack, 4U) x 290mm
Single5.5kg (12lb)
Triple10.5kg (23lb)

Rack MountRM410 19 inch 4U mount for up to three single output units or one triple plus one single. Blanking plates are supplied for unused sections.

Accuracy specifications apply for the temperature range 18°C to 28°C after one hour warm-up.

Thurlby Thandar Instruments Ltd. operates a policy of continuous development and reserves the right to alter specifications without prior notice.