PIL 40-121 Series Switched Relay Module SPST

The PIL 40-121 series is Pickering Interfaces' low-leakage-current PXI switching module series for semiconductor parameter testing. Its core differentiator lies in its switched-guard design, achieving an isolation resistance of up to 10¹³ Ω, specifically designed for low-current drive protection measurement environments such as WAT (Wafer Acceptance Testing). This series includes four models, covering both SPST general-purpose switches (13/26 channels) and 2:1 multiplexers (8/16 groups) topologies.

Compared to the manufacturer's high-density general-purpose reed relay series (such as the 40-140B), the PIL 40-121 Series Switched Relay Module SPST has a distinct positioning: the former prioritizes channel density and universal switching capabilities, while the latter focuses on ultra-high isolation resistance, targeting the niche scenario of low leakage current measurement at the nA or even pA level. This difference is reflected in several dimensions, including connector selection (MS-M RF vs 200-pin LFH), switching voltage specifications (100V vs 150V), and whether or not protection circuitry is included.

In terms of software ecosystem, the PIL 40-121 series fully covers Windows, Linux and real-time operating systems, and provides four driver types: VISA (pipx40), Direct I/O (pilpxi), IVI-C (pi40iv) and .NET. It is compatible with mainstream test and development environments such as LabVIEW, LabWindows/CVI, and TestStand, and is fully compatible with NI Switch Executive.

MXTD

Xi'an Mingxi Taida Information Technology Corporate Profile

For more than 12 years, Xi'an Mingxi Taida Information Technology Co., Ltd. has been a trusted innovator in the precision testing and industrial intelligent technology industry, empowering global enterprises with reliable, high-performance technical solutions. The company adopts an integrated business model that unites independent core R&D, global cross-border trade, and full-cycle professional technical services, delivering one-stop industrial support for modern intelligent manufacturing and engineering inspection scenarios.

Rooted in advanced industrial measurement and electronic technology research, MXTD focuses on the R&D and manufacturing of high-end test equipment, PCIE/PXIe modular boards and core electronic components. We have built a comprehensive product portfolio covering professional measuring instruments and industrial supporting equipment, fully optimized to adapt to complex and harsh industrial application environments, ensuring stable and efficient operation in high-precision testing and mission-critical industrial scenarios.

Boasting a global business layout, our sales and service network covers four continents including North America, South America, Europe and Africa. By integrating self-developed core technologies and exclusive distribution resources of world-renowned industrial brands, we streamline the global procurement supply chain and provide customers with standardized product supply, customized solution design and efficient global delivery services.

Quality is the core cornerstone of MXTD’s global development. Every product undergoes rigorous standardized inspection, precision calibration and multi-scenario environmental testing before delivery. We adhere to strict quality control standards in every production and service link, delivering highly stable, accurate and durable industrial equipment to help global customers reduce operational risks and create sustainable industrial value.

Product- PIL 40-121 Series Switched Relay Module SPST

The core positioning of this series is to provide signal switching solutions with ultra-high isolation resistance for low-level measurements and semiconductor parameter testing.

Unlike standard PXI switching modules, each signal path in the PIL 40-121 Series Switched Relay Module SPST is equipped with a synchronously switched guard path. This design significantly reduces the impact of leakage current and stray capacitance, increasing inter-channel isolation resistance to the order of 10¹³ Ω. This is at least four orders of magnitude higher than conventional reed relay switching modules (the off-state resistance of conventional reed relays is typically in the 10⁹ Ω range).

The PIL 40-121 series belongs to Pickering's low-density segment within the General Purpose PXI Relay Switch category.

As part of the switch protection product family, the PIL 40-121 Series Switched Relay Module SPST , together with the following products, forms a complete matrix of low leakage current switch solutions:

• 40-590 / 42-590 series: PXI / PXIe switch protection matrix modules (8×4 or 16×4 configuration)
• 65-290 series: LXI switch protection matrix modules (based on the 65-200 chassis, up to 6 plug-in modules)

The core value of the PIL 40-121 series can be summarized in the following three points:

• Ultra-high isolation resistance. Through the switched guard design, the module achieves an isolation resistance of up to 10¹³ Ω (point-to-point, with drive protection, 10V drive, 21°C, 40% RH conditions), a leading figure among PXI switching modules, sufficient to support accurate measurement of pA-level leakage current.

• High-quality reed relays. The entire series uses ruthenium sputtered reed relays manufactured by Pickering Electronics (the relay business unit of the Pickering Group). These relays offer long life, low contact resistance, and excellent contact resistance stability in low-level switching applications. Spare relays are also provided on the circuit board for quick maintenance.

• Quick-connect design. The PXI PIL 40-121 module uses a multi-channel MS-M connector. In SPST configuration, all 52 pins are distributed between two connectors, significantly accelerating connection and disconnection operations. This is especially important for test stations that require frequent assembly and disassembly.

The Key Value of The PIL 40-121 Series Switched Relay Module SPST

Differentiation advantages

The core differentiator of the PIL 40-121 Series Switched Relay Module SPST lies in its switched guard architecture. Compared to traditional switching modules, the fundamental difference is that each signal relay is equipped with a synchronously acting guard relay. As the signal path switches, the guard ring also switches, ensuring that the area around the signal path remains in an equipotential protection state, thereby reducing leakage current to extremely low levels. The trade-off for this design is double the number of relays (each channel requires a bipolar relay), but in return, it results in an order-of-magnitude improvement in isolation performance.

Comparison with the 40-140B high-density reed relay series from the same manufacturer:

The comparison reveals that the PIL 40-121 Series is not designed for channel density or switching speed—it sacrifices some density and speed in exchange for irreplaceable isolation performance in low leakage current measurement scenarios. For general signal switching applications, the 40-140B and other general-purpose series offer advantages in cost-effectiveness and density; however, when testing objects involving pA-level current, fA-level leakage current, or TΩ-level insulation resistance, the switched guard design of the 40-121 becomes a necessary choice.

Compared with the 40-590 matrix switch module

The 40-121, 40-590, and 42-590 all belong to the Pickering switch protection product family. Their main differences lie in their topology and expansion methods:

• 40-121: SPST / 2:1 MUX topology, MS-M multi-channel connector, no loop-thru expansion function, PXI platform only.
• 40-590 / 42-590: Matrix topology (8×4 / 16×4), MMCX miniature coaxial connector, supports loop-thru X-axis expansion, provides both PXI and PXIe platforms. The choice of series depends on the signal routing requirements of the test system: the 40-121 is suitable for point-to-point or simple multiplexing environments, while the 40-590 should be selected for scenarios requiring cross-point matrix routing.

The PIL 40-121 Series Switched Relay Module SPST was released alongside the 40-590 / 42-590 matrix switch modules and the 65-290 LXI matrix module, together forming Pickering's first complete low leakage current switched guard product series.

The launch of this product line directly addresses the growing demand in the semiconductor industry for low-current drive protection measurements. In wafer acceptance testing (WAT) of advanced processes, the accuracy of leakage current measurement directly impacts the effectiveness of process monitoring, and leakage current in traditional switching modules is often a major source of measurement error. Pickering's entry into this niche market at this time is both a response to the evolving needs of semiconductor testing and a synergistic advantage built upon its vertically integrated relay manufacturing capabilities within the group.

Product Lines and Generational Relationships

The PIL 40-121 series belongs to Pickering's first-generation switch protection PXI modules. From a technical perspective:

• Previous products: Pickering had previously produced several low-level switching reed relay modules (such as the 40-110/115/120/125 series and the 40-140 series), but none of these products adopted a switched guard design, and their isolation resistance was at the level of conventional reed relays (in the order of 10⁹ Ω).

• Current product: The PIL 40-121 series represents Pickering's first introduction of a switched guard architecture on the PXI platform, raising the isolation resistance to the 10¹³ Ω level, specifically targeting the semiconductor parameter testing market.

• The same generation of horizontal products: 40-590 / 42-590 (PXI/PXIe matrix) and 65-290 (LXI matrix) constitute a complete product matrix of switch protection products.

The core function of the PIL 40-121 series is to provide high-isolation-resistance signal switching with switch protection in PXI test systems. Specifically, the functional positioning of each model is as follows:

SPST versions (40-121-001 / 40-121-002) provide 26 or 13 independent single-pole single-throw switch channels, each with a corresponding protection path. By default, all signals and protection paths are disconnected. When the relay is energized, a signal path is established between terminal C (common) and terminal A, and the corresponding protection connection is closed synchronously.

The 2:1 multiplexer version (40-121-011 / 40-121-012) provides 16 or 8 independent 2-to-1 multiplexers, each consisting of two bipolar reed relays—one controlling the CHx.1 signal path and the other controlling the CHx.2 signal path. Each signal path is also equipped with a synchronously switched protection path.

The core technology of the PIL 40-121 series is the switched guard architecture, whose working principle can be understood from the following aspects:

• Double-pole relay structure. Each reed relay used in the module is a double-pole structure—the first pole is used to switch the signal path, and the second pole is used to switch the corresponding guard path. The two poles are physically integrated inside the same reed relay to ensure a high degree of synchronization of action.

• Synchronous switching mechanism. When the relay is energized, the signal electrode and the protection electrode simultaneously engage: the signal electrode establishes a signal path from C to A, and the protection electrode simultaneously establishes a corresponding protection loop path. This synchronous switching ensures that at any point on the signal path, the surrounding protection structures are at the same potential, thereby greatly reducing leakage current between the signal path and ground, and between different signal paths.

• Electrical isolation architecture. Internally, a digital isolator isolates the PCI-side control signals from the relay driver side, further ensuring that the high isolation performance of the signal path is not compromised by the common-mode current of the control circuit. The functional block diagram shows that the control signals output from the PCI Bridge first pass through the digital isolator U9, then are sent to the relay drivers U10 & U11, ultimately driving the reed relay array.

• Power Supply. The module is powered by the +3.3V and +5V power supplies on the PXI backplane, with +3.3V consuming 250mA and +5V consuming 500mA. The +12V and -12V power supplies are not used, consistent with the module's design which uses only low-voltage reed relays (typically with a 5V coil).

Platform Compatibility

The PIL 40-121 Series Switched Relay Module SPST is a standard 3U PXI module, compatible with the following platforms and chassis types.

• Standard PXI Chassis: A 3U chassis compliant with PXI specifications.
• CompactPCI (cPCI) Chassis: Since PXI is based on the cPCI standard, the module can be used in a cPCI chassis.
• PXIe Hybrid Slot Chassis: The module can be inserted into a hybrid compatible slot (peripheral slot) in a PXIe chassis.
• Pickering LXI Modular Chassis: Can be used in Pickering's LXI or LXI/USB modular chassis for Ethernet control.

Note that the 40-121 series is only available in a PXI version; there is no native PXIe version. For switch protection modules for PXIe platforms, the 42-590 series should be selected (but this series is a matrix topology and does not offer SPST or 2:1 MUX configurations).

SPST version detailed configuration

The 40-121-001 (26x SPST) is the SPST configuration with the most channels in the series, integrating 26 independent protected SPST switches on a single-slot PXI module. Each switch is a bipolar reed relay, simultaneously switching signal and protection paths. The front panel features two 26-pin MS-M RF male connectors (J2 and J3), with a total of 52 signal pins distributed between the two connectors for easy quick plugging and unplugging. Spare relay positions are provided on the board for easy field maintenance.

40-121-002 (13x SPST) is a low-density version of the SPST configuration, providing 13 independent switching channels using only one 26-pin MS-M RF connector (J2) on the front panel. As can be seen from the relay number table in the user manual, model -002 uses the same PCB design as model -001, except that the relay is not installed at the second connector location (marked "Not Fitted"), reflecting the product configuration strategy of Pickering's flexible manufacturing line.

In the SPST version, each channel establishes a signal path from C (common terminal) to A terminal when the relay is energized, and simultaneously establishes a corresponding protection path. By default, all channels are disconnected. The module uses a sub-unit to control all relays, and the switching state of any channel can be controlled through bit operations.

Detailed Configuration of 2:1 Multiplexer Version

The 40-121-011 (16x 2:1 MUX) provides 16 independent 2-to-1 multiplexers, each containing two bipolar reed relays—one toggles the CHx.1 input to common terminal C, and the other toggles the CHx.2 input to common terminal C. The two relays operate mutually exclusively (only one can be active at a time), ensuring 2:1 selection functionality. The module uses a total of 32 bipolar reed relays and features two 26-pin MS-M RF connectors on the front panel.

The 40-121-012 (8x 2:1 MUX) is a low-density version of the multiplexer configuration, providing 8 2:1 multiplexers using 16 bipolar reed relays and equipped with only one 26-pin MS-M RF connector. Similar to the SPST version, the -012 model is also based on the same PCB platform, with unfitted relay locations marked "Not Fitted".

The multiplexer version is architecturally slightly more complex than the SPST version, additionally including a relay counting memory (U12) to record the number of times each relay operates. This is valuable for predicting relay life and planning maintenance. Furthermore, the multiplexer version uses two digital isolators (U9 and U13) to meet the isolation drive requirements of more relay channels.

Environmental Specifications

Software User Manual

The PIL 40-121 series supports multiple driver types to adapt to different programming environments and application requirements. All drivers are provided and maintained by Pickering:

Customization Services

Standard, off-the-shelf products rarely meet highly specialized technical requirements. To bridge this gap, our expert engineering team delivers comprehensive, built-to-order OEM and ODM customization services around your precise specifications. Whether you require customized frequency ranges, specialized triggering mechanisms, or tailor-made structural enclosures, we collaborate openly with you to build the ideal product. Our flexible engineering approach guarantees that your unique application goals are met without ever compromising our strict quality benchmarks.

The PIL 40-121 Series Switched Relay Module SPST is highly focused on testing scenarios requiring extremely low leakage current and ultra-high isolation resistance, primarily including:

• Semiconductor manufacturing testing. This is the primary target market for the 40-121 series. In wafer acceptance testing (WAT), chip parameter testing, and reliability testing, precise measurements of MOSFET leakage current, gate leakage current, and junction leakage current are required. These currents are often in the nA or even pA range, and any additional leakage current from the switching system directly affects measurement accuracy. The 10¹³ Ω isolation resistance of the 40-121 means that at a 10V test voltage, the leakage current introduced by the switch is only about 1 pA, far lower than that of conventional switching modules.

• Front-end of precision measurement instruments. In multi-channel scanning systems of precision measurement instruments such as picoammeters, electrometers, and high-resistance meters, the 40-121 can act as a signal selector, sequentially connecting multiple test points to the instrument while ensuring that the switch itself does not introduce significant measurement errors.

• High-impedance sensor testing. For testing high-impedance devices such as MEMS sensors, piezoelectric sensors, and electrochemical sensors, leakage current in the signal path directly affects the measurement lower limit. The 40-121 switch protection design effectively reduces leakage current and improves the sensitivity of the testing system.

• Materials science research. In research scenarios such as resistance measurement of insulating materials and low-current electrochemical measurements, extremely high requirements are placed on the isolation performance of the switch system.

FAQs:

Q: What is a Switched Guard, and how does it differ from a regular shielded guard?

A:  

A standard fixed guard ring has a fixed potential; the 40-121 is a switch-following guard ring: when the signal channel is closed, the corresponding guard channel closes synchronously to follow the signal potential; when the channel is opened, the guard opens synchronously. Purpose: To minimize parasitic capacitance leakage current on the board and achieve ultra-high isolation resistance, suitable for pA-level weak current testing.

Key point: The guard must be externally connected to the guard output of the source measurement unit (SMU); connecting it only to GND will significantly reduce isolation performance.

Q: Is it okay to use only the signal channel instead of the Guard channel?

A: 

The hardware allows it, but it will lose the high-impedance isolation specification, the leakage current will increase significantly, and it will no longer meet the 10¹³Ω isolation requirement; it is not recommended to leave the Guard circuit idle in weak current testing scenarios.

Q: When using a 40-121 to measure weak current, the leakage current is too high and does not meet the specifications?

A: 

Troubleshooting sequence:

• Guard wiring errors: SMU Guard not connected, Guard left floating, direct grounding;

• Cables: Triax cables must be used; ordinary BNC/coaxial cables cannot achieve Guard drive;

• Environment: High humidity (recommended <45% RH), panel connector contamination, ESD;

• Preheating: Reed relay thermoelectric potential stabilization requires more than 5 minutes of preheating;

• Procedure: Increase setup time after channel switching; for weak measurements, ≥200ms is recommended.

Q: Is it possible to hot-swap capacitive loads and semiconductor wafer capacitors?

A: ​​​​​​​

Avoid hot switching of capacitive loads while the capacitor is energized; the charging and discharging shocks of capacitors can cause contact arcing, shorten relay life, and in severe cases, cause contact adhesion. Prioritize: discharge first → switch channels → then apply voltage.

Q: What is the expected lifespan of a relay?

A: ​​​​​​​

Small signal cold switching (low current, no arc) can reach tens of millions of times; the lifespan drops sharply when approaching 1A high power hot switching; the advantage of ruthenium sputtered contacts is that the long-term stability at low levels is better than that of ordinary reeds.

Q: Explanation of common error codes

A: ​​​​​​​

• ER_NO_CARD (1): Incorrect card number/slot number; the system cannot find the card.
• ER_BAD_SUB (4), ER_BAD_BIT (5): Channel number exceeds the range of this model (e.g., writing >13 channels to model 002).
• ER_WRITE_FAIL (14): Communication failure; card disconnected, slot poor contact.
• ER_EXCESS_CLOSURE: Some topologies have channel mutual exclusion restrictions (MUX versions cannot simultaneously multi-channel select the same common terminal).​​​​​​​

Q: Is it possible to switch between high voltage (close to 100V) and pA current simultaneously?

A: ​​​​​​​

The maximum voltage specification is 100V, but the dielectric leakage current will increase under high voltage; for ultra-high resistance measurement, it is recommended to reduce the operating voltage as much as possible and optimize the triaxial wiring.

Contact Us

Ready to integrate reliable Switched Guard Relay Module control into your system? Our team is here to help you select the right configuration and provide ongoing support.

Contact our technical specialists at manager03@mxtdinfo.com  / manager02@mxtdinfo.com for detailed specifications, pricing information, or to discuss your custom requirements. We're committed to delivering the perfect PIL 40-121 Series Switched Relay Module SPST solution for your application needs.